Welcome!!
We will try to help you but can you give a little more information? How old is the chicken? How long has it been doing this? Is it getting progressively worse? Are there other symptoms such as wheezing, sneezing, nasal discharge, or open-mouth breathing? These are some of the more common symptoms of one of any number of upper respiratory ailments.
First, and formost, separate it from the rest of the flock. Once an infected bird drinks/feeds from a community drinking trough, it leaves behind the bacteria through its nasal discharge. Water also becomes contaminated by feces that end up in the water and also through the dust in the air that contains bacteria and settles into the water/feed. Simple contact with other birds and the aerosol droplets of bacteria in the air caused by infected birds are also a common means of transmission of the disease.
Your kids won't get sick but I wouldn't let them handle it for fear of contamination to the others.
Do some chicken watching and observe any unusual behavior. Also, one more strange thing to do look closely at the nasal openings and make sure they are open. Maybe, hopefully, this is something that will pass in a few days. But just to be safe.....isolate.
Maybe someone else has some ideas.....
Claudia