score:2
You should call your airline ASAP.
It is most likely the airline will automatically rebook you on a new itinerary, which could potentially involve them moving both your Europe -> Hong Kong and Hong Kong -> Manila flights to a later date. If you were to turn up to try and catch your original Europe -> HK flight you may well find that you no longer have a booking on that flight on that day.
If you call, they should be able to arrange whatever works best for you, which could include flying into HK on your original dates, and then MK->Manila at a later date (even if you don't end up taking that flight), or potentially re-routing you to a different final destination altogether.
If you were to cancel the final HK->Manila flight, then whether you would be allowed fly to Hong Kong would depend on your nationality and whether you hold a visa. Citizens of some countries require either a visa or an onward ticket in order to fly to Hong Kong, so if such requirements existed for you and then didn't meet them, then you would not be allowed board your initial flight.
Upvote:2
As Doc wrote, you should call your airline.
If your last leg is cancelled, they will most probably not let you fly the first leg and cancel it as well: if they let you fly to Hong Kong, they would have to provide assistance for you (pay for hotels and meals) while you're stuck there, and they most probably don't want to do that.
Airlines usually have special conditions in such situations that allow for free cancellations and changes to your flights even when they are not refundable or modifiable. Some airlines are able to handle this online directly, others may require you to call them to make changes to your booking in such cases.