Child Burned The Roof Of His Mouth. Din't Heal. It Caused Saliva & Discomfort. Biopsy Is Normal. Suggestions?

My son had the roof of his mouth burned three years ago and it didn't heal....it caused saliva and discomfort...spitting and slurping all the time...he had a biopsy and nothing was wrong (no cancer) but now there is a big hole there and it's irritated all the time...he didn't have insurance at the time and was in a different location. I sent him to UCLA oral surgery dept and they said there was a nerve problem and recommended either to cut the nerve or have a retainer made to support anesthetic ..he is so freaked by the biopsy creating the hole that he doesn't want anymore cutting...He has moved now and does have insurance....the dr. that he recently saw put him on cymbalta for the nerve situation and it's causing so much difficulty...he's having panic attacks and anxiety and blistering from the sun....I want him to go to a new dr. and see about the cutting of the nerve but don't know what kind of a dr. does this kind of thing...can you tell me what kind of dr. to seek out? He's in the first year of his marriage and his life has been miserable for him and his wife....The dr is going in the direction of upping the dosage on cymbalta and prescribing xanax for anxiety and I just think it's ridiculous...it's the mouth that's causing all the problems.....thank you for any help you many give.