If you haven't brought him inside, you will need to. He has two issues going on and he will likely need to be separated from his coopmates to recover. The frostbite will go through several stages of healing- first the burned stage, then the weepy stage, then the drying and sloughing stage. The areas will hopefully heal up without any major intervention. Keep the legs clean and coated in Neosporin. You will need to re-apply the ointment often to keep the legs covered. I would use some towels as bedding in his recovery cage to keep shavings and straw out of the wounds. You will need to keep the cage very clean to prevent infection in both the legs and the chest wound. He is going to be laying on the chest wound, so it is going to take a while to heal up. The legs should stop being oozy in a week or two. The swelling will go down at the same time. A light touch of frostbite should heal in about a month with the damaged tissue withering up and falling off. A worse case of frostbite may cause the chick to lose some toes. If this should happen it's not something to panic about. Chickens survive without toes all the time. Roosting may present some challenges, but overall a bird with lost toes will be OK. The toes will start to get dark and dried up looking. Keep applying the Neosporin (carefully so as not to break off a toe prematurely) and wait until the toes fall off by themselves. I don't advocate chopping into living birds to remove frostbitten areas. The areas will frequently fall off on their own, the risk of infection is quite small if you practice good hygiene and wound care, and I just hate deliberately inflicting pain if I can avoid it. The chest wound can be treated with the Neosporin, as well. That should be okay as long as the chick has no internal damage. A little bandage on the chest wound (gauze pad wrapped with Vet Wrap/Coban) may help to heal that up a little faster. It is going to get irritated and take longer to heal if the chick is laying on it.
I hope this helps. Keep us posted on the chick's progress.
