Sorry! I must've been tagging you at the same time your post came through. I knew you'd know what was going on. Thank youHe has frost bite on his toes and a bit on his comb. It looks like it has been there for some time. Parts of the foot and the toe tips may slough off in the coming weeks. The comb should be fine, though some points may become rounded off. If he was brought in where it is warm, you could do some warm soaks in Epsom salts water daily, and then spray it with Vetericyn Hydrogel spray. Here is some reading:
https://the-chicken-chick.com/frostbit-in-backyard-chickens-causes/