It does look a little swollen where that wound is it may not have anything to do with him folding his foot but I would treat it those types of wounds can get infected. You can clean it real good using warm Epsom salt water then dry and use an antibiotic ointment on it without pain relief wrap it for a few days to keep the foot dry and give the ointment time to work. where his foot is folding you could try making him a boot to keep his foot flat. Since he isn't walking, this could be from not getting enough exercise, and the muscles are weak but a boot can help You can take something like a cool whip container or butter container etc lay the foot flat on the container make an outline of the foot then cut the plastic wrap with some type of tape or vet wap lay the foot onto the boot then wrap with vet wrap to keep the boot on and the foot flat go up the leg with the wrap to keep him for getting it off they are pretty good at it. This will also help to keep the wound wrap from getting dirty. Are you still getting the wheel chair? working to keep his foot flat in normal position will help he better maneuver the chair when he starts using it.