Have him sit down and firmly pinch the soft part of his nose, just above his nostrils, for at least 10-15 minutes. Have him lean forward and breathe through his mouth – this will drain blood into your nose instead of down the back of your throat. Place an ice pack or bag of frozen vegetables covered by a towel on the bridge of his nose. Have him stay upright, rather than lying down, as this reduces the blood pressure in the blood vessels of your nose and will discourage further bleeding. If he is under two years old take him to the hospital. If he is older than two, figure out if his nose is broken by seeing if he has pain around his nose combined with swelling, bleeding, and/or bruising around the nose or eyes.
