You should remove the bone. It'll press against the skin when he moves and cause pain and sores. Make sure you numb him up. Is there any necrosis? Any drainage? When you remove the bone, go ahead and take something sharp against the leg tissues. It might help better if pink healthy tissue is exposed verses mostly dead tissue. The arm probably didn't heal right, but if it doest seem to be causing him any issues I'd just leave it. If you could somehow get an x-ray of that area, that would really help and you ideas. I know that might be practically impossible though.