Ow, ow, ow. Enjoy.
I've gotten those damn things for years. The only thing that helps: time. About two weeks.
It can be something as mild as a potato chip abrading my tongue, or the inside of my mouth, and it'll open into a sore, sometimes nearly a quarter inch wide.
I've asked doctors, dentists, and an orthodontist about solutions. I've tried "home remedies," and some prescriptions. Nothing helped. They've gotten better over the years though. When I was in middle and high school, I'd rarely go a few days without one. At the worst, I had 7 at once. Now I might go a full week without one. I've heard theories about their cause ranging from a virus of some sort, to some kind of defensive enzyme deficiency in my saliva.
All I can really do is numb the pain away, and the best I can get is Orajel, 20% benzocaine. Sometimes it gets bad to the point that I'd just love a Novocaine shot so I could eat without the pain - 20% benzocaine just doesn't always do the trick. And I hate injections, just in my skin. I've never had one in my mouth.