Seriously? Stomatitis/mouth rot is an infection and it's not just going to go away on it's own, especially not in a chameleon (who take forever to heal from anything). Any vet should know this.
I don't know if you can find this in a store that sells horse goods, but I was given an astringent mouth wash that was for horses and dogs, called Chlorehexidine flush. You don't need a prescription, it's just to help dry out the mouth when you wash with it and it'll make conditions harder for the bacteria to live and thrive in. With my Meller's chameleon it really made a difference. I would clean with a Q-tip soaked in it and then take guaze, get it wet, and dab the entire mouth on the inside, focusing on the gum lines in particular and the roof of the mouth.
Obviously, I needed held holding her mouth open and volunteered my father. So you might have to call in a friend or family member to help. Unless he's a really good gaper, and he'll probably hold it open for you alone!