Hi there! You should definitely not try to remove any of the tissue unless it falls off on its own. Some people have good results using an iodine dip to disinfect, but this should be researched as I’ve never done it myself. If the mouth is damaged, don’t try to feed it until it grows back. If it is not damaged, still do not feed it for at least a week or two of improvement.
During the recovery, you will need to keep the water clean. The parts that die will rot quickly so you will need to stay on top that. Regular/frequent water changes are best for this, depending on your tank size.
If the damaged area starts to look fuzzy like cotton candy, that is a bad sign. Medical treatment may be your only hope at that point. When areas that are not damaged start to get covered with this cloudy fuzz, it almost 100% too far gone. I’ve never heard of one recovering after that.
I hope this helps, and good luck!