The scales involved are the internasals, prefrontals, frontal. If I were you, I'd go to the vet and get some SSD Ointment (1% Silver Sulfadiazine Cream). Put that on once a day until he sheds a couple of times. You should see him shedding at an accellerated rate trying to heal that. It should be OK after a few sheds.
I have a large male Texas Indigo that was missing the nasals, internasals , parts of the prefrontals and a couple of superlabials when I got him. It was through no fault of the person I acquired him from because he was in the same condition when he aquired him. Apparently the owner before him kept him in a cage that was too small and had too much wire mesh or something. At any rate, I started using SSD on him daily until he shed twice. It helped him form some granulated type scar tissue and now, every time he sheds, he seems to get a little more scalation back. I also put him in a large cage (6ft x 2ft x 2ft) with plenty of hiding options and he doesn't seem to feel the need to rub his nose any more. When I first got him, he would bleed profusely for about 3 days after every time he shed, but now that's gone. He absolutely hated the routine every morning and was hatching a plan to kill me while I was treating him. He was pretty sure that if he could get me down on the floor, he could chew my head off...if that didn't work he had an alternate plan to drown me in his water bowl. Now that his nose is getting better, he has forgiven me and he only wants to chew one of my fingers off.