If his feet are frozen all the way through, he may lose them. But if they are partially frozen, you might be able to save them. Be sure that your coop is dry and the bedding is thick. Clean up any water spills. Here are some good articles about frostbite:
https://the-chicken-chick.com/frostbit-in-backyard-chickens-causes/
https://articles.extension.org/pages/70255/frostbite-in-chickens
http://www.poultrydvm.com/condition/frostbite
https://the-chicken-chick.com/frostbit-in-backyard-chickens-causes/
https://articles.extension.org/pages/70255/frostbite-in-chickens
http://www.poultrydvm.com/condition/frostbite