I haven't scoped a vet yet - I'm going to do that today.
The confusing part is that he has two issues going on - the necrosis, which is either gone or considerably less, and an impact injury, which is where I think (hope?) that the swelling is coming from.
If anything, the swelling has gone down a bit since that pic, so I'm continuing to monitor and research local Herp Vets.
Thanks again to everyone for their support/input!