Mouth sores or "aphthous ulcers" can be very painful and make eating difficult. They usually resolve in 7-10 days but until then there are some things you can do to relieve your discomfort.
DO continue to brush your teeth regularly -keeping down the amount of germs in your mouth will allow the sore to heal faster.
USE a peroxide type mouth rinse like Peroxyl not alcohol based like Listerine. Alcohol based mouth rinses will irritate the ulcers & make them more painful. Peroxide type mouth rinses will cleanse and soothe the ulcers and allow them to heal faster.
DO take whatever you normally take for a headache to ease the pain (as directed-never take more than the label says... even over the counter medicines can be dangerous if taken improperly-even deadly!!!!).
DO NOT put the pain medicine pill on the ulcer-swallow it. Putting aspirin on mouth sore is an old wives' tale and can make it severely worse!
DO use an ointment recommended for mouth ulcers like orabase or benzodent to ease the pain-apply it before eating to make it more comfortable.
If you have an ulcer that does not hurt and does not go away within a week-see your dentist immediately-it could be an early sign of another medical problem. If the painful ulcers continue to recur your dentist can make other recommendations to help.