From other posts I've seen here, it might be frostbite. I am still learning about this subject myself. Are you from a cold location? Would frostbite be a possibility? As far as treatment, I can't help you on that. You might do a search on "frostbite treatment".
You can't really treat it. Just lather it in vaseline, that's not supposed to freeze. My roos are getting it too. Crumby week weather wise.
I've read that massaging helps get the blood flow circulating again and might help. Will he let you get a hold of him and rub his comb?