You don’t need to have a visa to visit Nicaragua. The only request is that you buy a tourist card for $10 and have a valid passport.
You can find more detailed information in this link, it is pretty acquire. The US embassy has good service for Americans in this country and good Facebook page.
According to the Bureau of Consular Affairs:
A visa is not required for U.S. citizens; however, a tourist card must be purchased for $10 upon arrival. Tourist cards are typically issued for 30 to 90 days.
You can see all pertinent information here. It is accurate.
Credit:stackoverflow.com‘