That's been brewing for longer than a day. There is granulation tissue at the edges of the wound (that ridge of skin), which takes several days to form. I suspect the top of his casque might have been burned by his heat lamp and then the dead skin rubbed off on a branch yesterday because it was already damaged. Keep it clean and put neosporin on it twice a day and take him to the vet if it starts to look worse or has discharge.