The first thing to do is to rinse your mouth a few times a day with very warm salt water. You could alternate this with rinsing your mouth with 3% hydrogen peroxide. If you have a waterpik, use it a few times a day. If this doesn't help after a few days, then see your dentist. You might have an infection of the gums, or perhaps some tooth decay. Also take plenty of vitamin c and 50mg a day of zinc.