What if you "forgot" your passport?
The article is about Ecuador, not Nicaragua, but it does offer something to think about. It is about a woman who flew to Ecuador without her passport and what happened.
The article is in The Washington Times.
QUITO, Ecuador—An American senior citizen on a flight to South America was seized and jailed by Ecuador immigration authorities after arriving there for a vacation.
The article at least implies that Ecuador mistreated her. If they did it was because they followed the law. It doesn't matter that she was a senior citizen, was on vacation or anything else. What it does do is give anyone traveling something to think about.
For whatever reason, let's say you arrived in Managua without your passport. What would happen? Would you get tossed in jail? Would the embassy of your country in Nicaragua help you solve the problem?
My understanding is that if an airline delivers you to a new country without the documents to clear immigration then they are responsible for returning you to where you came from. In her case, that did not happen and the airlines apparently said it was not their problem.