Perhaps just the fact that it's JJ's hand explains it but not so much in the game. IIRC back in the first half of Season 1, Jesse's hand had all fingers. Then at some point, a finger ends up missing all of the sudden. There were even some threads on it then but I don't recall the replies.
Was there ever an explanation (in the game) as to where his finger went (yet)?
When I was playing through 205, there was a scene that made me think that there would be an explanation but no. Is it a "did you try..." moment? or will it be one of those ongoing mysteries that will be revealed somewhere in season 3? Or did I just totally miss it?