Is it necessary to be socialize to understand dhamma?

Case 57 of the Blue Cliff Record
I Alone Am Holy

A monastic said to Zhaozhou, "It is said, 'The real Way is not difficult. It only abhors choice and attachment.' Now, what are nonchoice and nonattachment?"
Zhaozhou said, "I alone am holy throughout heaven and earth."
The monastic said, "It is still choice and attachment."
Zhaozhou said, "You country bumpkin! Where are choice and attachment?"
The monastic was speechless.

If you're going to practice Buddhism, expect to have everything challenged. There's not a single thing about you that is going to go unexamined. All those soft places in your psychological underbelly will be prodded until you are sore, bleeding, and begging for mercy. This is the only way to wake up. All of your petty fears and preferences are way stations on the one going road to Buddhahood. Confronting them, gaining insight into them, and eradicating them is the very essence of the great way.

The great way is not difficult for those who have no preferences. When love and hate are both absent, everything becomes clear and undisguised. Make the smallest distinction, however, and heaven and earth are set infinitely apart...to set up what you like against what you dislike is the disease of the mind (from the Hsin Hsin Ming).

Of the two possibilities - being social and distancing yourself from others - which of the two is more difficult? Which of the two challenges you? Which would you rather not do? Pick the harder way. You alone are holy throughout earth and heaven but only when the barrier between you and others - when petty concerns of liking and disliking - dissolves. When that happens, who are you?

No it is just another life experience .Buddha did this because he was just starting the way ,so you can start like that but ultimately you have to interact with life .Actually sometimes its harder to be by oneself if one is used to socializing or not used to solidarity .So don't mind that ,just take it step by step .

So, Is it necessary to be socialize ?

Life would be difficult, even impossible, living completely alone. There is a reason that the sangha is considered one of the three jewels in buddhism.

If it is, Why buddha said, go to a forest to meditate ? Get a free and quite time ?

Yes. Your understanding is on point. Withdrawing into reflection is helpful for developing a buddhist practice from time to time.

If it isn't How do I recognize those thoughts ? (If we have no reason to get those feelings, we might think we haven't those thoughts)

Perhaps you are right, one could possibly avoid developing aversion in solitude. However, to a larger extent, it seems to have a tendency to foster a feeling of alienation. Too much time alone may make us less accustomed to relate to others, even though we may have good intentions.

In the noble eightfold path, right effort isn't just about preventing aversion to take a hold of us. It is also about developing skills that we may not have right now. Prosocial virtues, such as the brahmaviharas is most likely impossible to cultivate in complete solitude.

From Magga-vibhanga Sutta:

"And what, monks, is right effort? (i) There is the case where a monk generates desire, endeavors, activates persistence, upholds & exerts his intent for the sake of the non-arising of evil, unskillful qualities that have not yet arisen. (ii) He generates desire, endeavors, activates persistence, upholds & exerts his intent for the sake of the abandonment of evil, unskillful qualities that have arisen. (iii) He generates desire, endeavors, activates persistence, upholds & exerts his intent for the sake of the arising of skillful qualities that have not yet arisen. (iv) He generates desire, endeavors, activates persistence, upholds & exerts his intent for the maintenance, non-confusion, increase, plenitude, development, & culmination of skillful qualities that have arisen: This, monks, is called right effort.

https://www.accesstoinsight.org/tipitaka/sn/sn45/sn45.008.than.html

Or should I not think about that ? (Being social or not being social is out of my control ?)

It is likely within your control, and i believe it is a form of control that is beneficial, and not the clinging/grasping type of control.

Ānanda brought a similar question to the Buddha, attempting to hedge and bridge the issue of solitude and social interaction:

SN3.18:3.3: ‘Sir, good friends, companions, and associates are half the spiritual life.’

But the Buddha would have none of that and corrected Ānanda immediately:

SN3.18:4.2: ‘Not so, Ānanda! Not so, Ānanda! Good friends, companions, and associates are the whole of the spiritual life.

"Socialization" is conventionally conducted to seek and provide affirmation of individual identity or conformance to group identity. One compliments a hair style, for example. Or one suggests a current fashion of dress.

The purpose of the Saṅgha is different. The purpose of the Saṅgha is to support all those on the Noble Eightfold Path:

SN3.18:4.4: A mendicant with good friends, companions, and associates can expect to develop and cultivate the noble eightfold path.

That said, solitude does support deeper study. Indeed, AN4.138 details ways of accomplishing such retreat with body and/or mind.

AN4.138:5.1: And how is a person on retreat in both body and mind? It’s when a person frequents remote lodgings in the wilderness and the forest. And they think thoughts of renunciation, good will, and harmlessness.