I got the melting back idea from something that happend to me actually. I had a pretty bad fall due to a hotels neglegence, in which I scraped my right hand horribly on a cement sidewalk, with myself and a computer moniter on top of them. You could see the muscle on my middle right hand finger, that gives you an idea of how deep it was. Anyway, the way it was ripped open, we couldnt stitch it shut or anything. So I had to just keep it covered until it healed up. Whenever I went to change bandages, you could see what was essentially liquid skin, filling in the holes. It was pretty disgusting, and I think something to that effect would work. Here's my whole idea.
The flame from the back of his skull wraps around his head, and turns into muscle, then from the gaps in the muscle, the liquid skin slowly leaks out and covers him, some dripping off of course. Through it, his hair sticks out, and it then solidifies, and he's back to normal.