Whats the best way to treat a mouth ulcer?

Mouth ulcer: Most ulcers in the mucus membranes of one's mouth (and other surfaces) are expressions of Herpes virus , which are brought about by stress, (poor diet, lack of sleep, etc.) which activates the virus along nerve fibers. Ask your healthcare provider to prescribe antiviral medication, which can shorten or prevent new outbreaks.

See your Dentist: What you are calling an ulcer may actually be something else. Best to have your Dentist examine you and provide the best treatment. There are medications available that can help. Until you get to your Dentist, if it is truly an ulcer, dabbing a small amount of Orabase-B (the B is important) onto ulcer with a Q tip should take the sting out as the ulcer heals.

First: See your dentist and find out what is the nature of the ulcer and its probable cause. (S)he will then tell you how to treat it. If it turns out to be an aphthous ulcer (a cold sore), I like to recommend Chloraseptic liquid for relief of pain. It will not burn the tissue as Benzocaine will.

Lasers can help: If there is a dentist in your area that has a laser they can effectively shorten the healing time. Common canker sores (Sores not on your gums) are not caused by a virus but are an inflammatory reaction. Non laser treatments include topical steroid such as kenalog or a dentist applied chemical cautery known as Debacterol. More info-https://www.laserdentistbaltimore.com/mouth-ulcers-cold-sores-etc