doubleofive said:

Why would it need to be his hand?!

Yeah, it's been whatever it's been for 35 years. No one ever really complained. Everyone at some point or another was curious about what it is, but it's specific detail was never important to the scene. Luke fell, got stuck in a hopeless situation after hearing some traumatic news, and that's the point of the scene. It's him at his lowest point.

Really, who cares what is falling at that point? You're supposed to be caring about Luke and his situation in that moment.