what are you feeding? any changes in the tank (sg, temp, ect)? How does the rest of him look?
They can regrow legs, they can regrow almost all. I've seen it with brittle and serpent.
IME, leave it alone, see if it will eat, otherwise, leave it be.
I kept the lights off on half my tank when my brittle and serpents were in trouble. (tank went through a mini cycle), both kinda melted... neither ate for a long time (at least they didn't eat what I was feeding, must have just ate lr), both stayed in the lr, in the dark. Brittle took longer to get better, but he did and they were both as big/bigger than before. Sadly though, I lost my brittle during a bad sg swing, serpent is fine though, and looks great.