Confine him, is the only thing I can think of.
Our LuckyDuck (kitty) had a huge abcess on his throat when hubby rescued him. I mean almost tennis ball size. The vet had to cut a "Y" shape out of his neck-skin because the tissue wasn't viable. She put in some stitches, some ripped out and when he'd shake his head I could hear his neck skin flapping and getting air underneath! *shudders* We had a few more stitches put in and he did fine.
I wonder if perhaps he just needs some more stitches, closer together, so the wound will heal quicker? Maybe an Elizebethan collar to keep him from pulling at them with his teeth?