About 15min into the movie after Tom met with his doctor friend about his shaking hands there is discussion about his lost pointer finger on his right hand.

In the following scene where Tom is in his motel reminiscing about old times he grabs his old photo of him and his old army mate, firstly, he grabs it with his left hand and upon change of camera he is holding it with his right hand (although it is possible he put it into his right hand) however when holding it with his right hand you can clearly see that he has all 5 full fingers instead of 4 and a half (the half being his pointer finger).

You'll also notice that later in that same scene (after he finishes looking at the first batch of photo's) he takes a swig of whiskey and you can see his finger tucked in behind his others to give the illusion of the missing finger.

Nothing too major but still a small slipup.