See a dentist. Treatment of sores in the mouth can vary dramatically depending on the cause of the sore. So it's wise to see a dentist or physician to diagnose and suggest an appropriate treatment. Cold sores can be controlled, but not cured. Until you can see the dentist/physician, keep the area clean with warm water rinses. If eating/drinking is painful, try bland foods.
Give it time. 5 to 10 days will do it.
Doctor can treat. Cold sores on or near the lips are herpes virus infections, and resolve in most people in a week. Oral antiviral drugs, such as Acyclovir and several others, are effective in preventing outbreaks of cold sores, decreasing the severity of sores, and shortening the healing time of sores. Topical lip balms with anti-viral abilities can help, but not as much as the oral medications do.
Time. There are no good cures for cold sores other than the fact that they will resolve spontaneously. Current medications, at best, work poorly.
Abreva. My patients get good results with an over the counter cream called abreva. It is expensive but works well. Apply to cold sore twice a day to shorten the duration. If the cream is applied as soon as you feel the 'tingly' sensation of a new cold sore, it can stop the sore from appearing.
Diode Laser. A diode laser will speed up the healing without drugs. You'll have to see a local dentist who is equipped with the laser. Http://www. Amdlasers. Com/media/articles/Diode_Laser_Treatment_of_Oral_Lesions. Pdf.