First time travelers to Nicaragua, especially, should take note on the following aspects. In general, Nicaragua is a very safe country but like any country there are chances that crimes might happen. You can reduce the chances of being a victim by taking to heart the following advices:
About strangers in your room
This is a very important piece of advice that you really should follow while in Nicaragua. While you are here, your hotel room or flat is your home. You should not take strangers you have just met back home with you, DON'T invite anyone you don't know or who hasn't been well-vouched-for to your hotel room. This is where you keep your valuables, documents, clothing, smartphone, camera, etc., so use your good sense; even if you do, be sure your valuables and other personal items are always put away out of sight. There's no need to tempt your guests.
Hotels do not have the obligation of letting you take visitors to your room. If they allow it, you must register this guest, and they should leave any valid personal ID at the front desk, to be claimed on the way out. After they have been checked, you are OK!. This is for your own protection, as the hotel will take your visitor's ID information as part of the process. People who've sneaked guests into their rooms have been known to regret it later!
Many lodging businesses are not flexible with non-registered visitors and arguing is pointless. They are following management directions, and everything these days is being taped for supervision. Many businesses are not gay-friendly either, so avoid taking several guests to your room, this may not be a good idea and might create problems. A better idea is to get together with your hot new acquaintances at a room-by-the-hour "motel" where you're less likely to have problems or be ripped off.