Hello,
I do see that bump there. Did he take a fall or get his arm wedged in between something & hurt it?
Are you using a good
UVB light for him & calcium supplementation?
If he isn't using the arm, then he definitely hurt his arm. If it appears to have been broken, the way it looks to me that would be very hard to set at home. I would highly recommend taking him to the vet for an x-ray. For now, if it seems to hurt him, try to keep him from climbing up things to bask so he doesn't hurt himself any further. So you may need to readjust his lighting distance so he still gets the adequate heating.
Let us know how he is doing.
Tracie