They do have amazing healing powers. You obviously need to seperate them and try putting antibiotic onintment on the wound. For further information by people more expert than I, Try posting this in emergencies.
For future reference. You can't add two groups of chickens together without first allowing them to get used to each other, either by a fenced off area or by placing a cage with the new birds inside the area with the established ones. This type of pecking is common when trying to intergrate two flocks. The should be kept at least two weeks seperated in the arrangement just mentioned before trying to intergrate them. The night is the best time to try to make the move.