I used to get them when I was a kid all the time, turns out eating too much sugar caused it. Sooo... wana know a cure? lol, I've asked around and I know more than all my doctors and dentists combined.


A really good one is this (only works for lips ones, I'm not even sure the little white tongue ones can be called cankers): Make sure the canker is wet with saliva, then quickly cover it in baking soda. It's going to hurt like hell, and the longer you keep it on the more it's going to hurt. But if you really wanna accomplish about a 50-75% healing, you'll do this (I have many times). But to make it work you gotta hold it on there for a good minute at least, a couple minutes ideally.
This seems to shink it, dry it out, and smooth out the surface. And best of all, it'll hurt about half as much! I've never tried doing it more than once to the same canker, but I don't think it would accomplish much to do so.

In the meantime, figure out what's causing you cankers. The most usual culprits for anybody are soda, candy, gluten (maily wheat), or chocolate.