Treat aphthae
Anyone who has had aphthae (google ...) knows how corrosive they are. A friend once gave me a tip that always helped against aphthae; the stuff is called "just 1 drop - natural oral care concentrate". (yes, with spelling mistakes).
Just drop a drop or apply it with your finger. Burns something and tastes so highly concentrated after nothing. But it helps!
Possibly. repeat two more days and then you have no more problems with it.
Achung: contains alcohol, so it's not for dry alcoholics!