Hello,
How long has he been favoring that arm?
Can you review the tank setup with us, so we can be sure it's all correct for him?
If you have a video of him trying to use his arm, that can help also. He looks very young, too.
I would recommend lowering his basking platform though, for now, so that he doesn't hurt him
self trying to climb up to bask, etc. So you may need to readjust his lights to be closer to him
for awhile also.
How is his appetite?
Tracie