That happened to one of my Jackson chams when I first got in the hobby. I can not remember what the exact name was but let’s go with mouth rot or something like that anyway the reason I am telling you this is because it was something like the version of cold sores in humans and the guy at the reptile rescue used a medicine for humans that you put on your lips and believe it or not it worked. I probably shouldn’t have told you that story and I wouldn’t recommend it but I was amazed lol.