I’m sorry this happened to your chicken. It can take a couple of weeks to see how much damage there will be. This is a good thread to read where it shows frost bite in a chicken with photos of the progression:
https://www.backyardchickens.com/ar...to-know-about-injury-care-and-recovery.78168/
https://www.backyardchickens.com/ar...to-know-about-injury-care-and-recovery.78168/