Clean it up using just warm water then dry as well as you can. Then I would squirt on a goodly amount of Aloe Vera Gelly ( I always use Forever Living Products which is a US which a vet told me about; he had huge successes with it on otherwise hopeless cases of open wounds and sores). You will have to repeat this every hour 4 or 5 times and it will start to heal almost in front of your eyes. It's amazing stuff! Thet do a line of the vetinary products but I tend to use the human stuff because thats what i have at home. If you got in touch with them I'm sure they would send infomation. I definitely wouldn't let him out till he's well scabbed up and then cover the comb with more aloe gel and a slather of Vaseline. The Andalusian cocks I used to keep were very prone to frostbite even here in the southern counties of England.