The nose is beautifully designed to function as a shock absorber, so that blows to the face do not injure the head. When the nose collides with a hard surface (e.g., your child runs into a sliding glass door, falls flat on his face, or is hit by a flying fist) the nose flattens as the thin nasal bones are pushed out each side. If these bones did not give easily in response to trauma, the pressure of the blow would be transmitted to the internal structures on the head.
When the nose gets banged, apply an ice pack for at least a half hour. Apply pressure with an ice pack on the bulged-out swollen areas on each side of the nose, just below the nasal corner of the eyes.