treat it like a burn.  That came from an Alaskan hospital where I was being treated for a hand burn, and a mountain climber was being treated for frostbite.  
Severe frostbite may peel.   turning black - see a doctor.   be very careful about infection.   light frostbite - I would suggest Vit E and aloe vera, (the real stuff). keep the skin as moist as you can with those products.