Ah, picture from the top-down helps. Now I see what you mean. So a few things you can try, unfortunately, they aren't guarantees...
50% Tankwater/50% Iodine dip
or hydrogen peroxide dip.
Rest the coral if you can in a low flow low light area, then watch an wait.
People have also had moderate success in removing their dying head and keeping the healthy one. I can't promise that any of these will work. Sadly this is part of owning torches