It's good news that he isn't skinny but inclined to think that they are either itchy or painful if he has opened them up himself, poor lad.
I will be interested to hear what your veterinary contacts suggest if you don't mind updating the thread. The only thing I would suggest is keeping them, clean and perhaps covering the open wound with a dressing and vetwrap/cohesive bandage. Another member on here recently had a large gaping wound on her hen that had been caused by a roosters spur. It was huge and horrific looking. She treated it initially with honey and then granulated white sugar under the dressing and she used stockingette to hold the dressing in place. It healed up beautifully. I can try to find the thread if you would like more info on that.