Children are curious individuals. They explore the environment around them, put their hands on all manners of objects with in their reach. Often, especially the young ones like to put small objects into their mouth, ear and nose.
There may not be any clear indication that this has happened.
Some signs that suggests that there may be something in the nose is a unilateral (one sided) nasal discharged, especially if this is yellow or green in nature and or nose bleeds. There may also be pain when infection occurs. If you suspect that there may be a foreign body in the nose, DO NOT ATTEMPT to remove it as it may push it further in and risk being aspirated. Instead bring the child to an ENT doctor who will be able to assess and remove the foreign body. In certain situation, if this is not accomplished in the clinic, one may have to do it under general anaesthesia.