Rinse your mouth with a solution of half a teaspoon of salt and eight ounces of water several times a day. If pain, sensitivity to hot and cold, and swelling exist, get to a doctor–it could be an abcess.
Rinse the tooth thoroughly with drinking water, then protect the sensitive nerve by placing a chewed piece of gum over the break. Apply a cold-water bladder to the patient's cheek to reduce swelling, and take ibuprofen for the pain. Hike out to your dentist.