Try bag balm. You can get it at cvs, and it heals it very quickly, and tastes icky, so he will be less likely to lick it. A friend of my daughters had this same habit, getting a huge red ring around her mouth every winter, and she got to the point that every time she came to stay a few days with us, she asked for the bag balm. By the time she went home, it would be cleared up. Her mom just used vaseline on it, and as I said, she would ask me for the bag balm as soon as she got to my house. Good luck.