With a little magic tweeeking with photoshop you can bring out some clues to wether it was photoshoped, if those modifications werent covered up. And judging by all the artifacts that now surface around the "finger" and hand, it looks like its indeed chopped.
The man was probably holding a heavy book vertically judging by the tight clench he has of his other four finguers (not a very natural thing when simply extending the 3rd finguer in the "finguer flick" and more characteristic of holding something heavy) and the horizontal and vertical artifactual lines extending from his palm laterally and upwards. You can make out the outline if you look closely.