Factual error: Shane's rank is Lieutenant but his formal uniform in the hospital after he gets shot shows the rank of Captain.
Factual error: When the Navy Seals land on the beach, Shane then gives a briefing on their target to capture and what to do. This is nonsense. A briefing would happen before they even left to do the mission, not as they started it in enemy territory. Being Navy Seals, they have a degree of intelligence, certainly enough that they wouldn't need a quick reminder as they start the mission.
Other mistake: When Shane is installing the security cam, he looks to verify the image, but we are shown a standard quality image that you would find in a typical security cam. If he was on a top priority project for the military, the video quality would be way above what we see. It would also most likely not look like an off the shelf video camera (i.e. it would likely be less detectable than what he put up).
Other mistake: The mom comes home and finds the Sound Of Music poster for the performance that her son is in. Louisa on the poster is a completely different actress from the one in the rehearsal scenes.
Other mistake: When Shane is in his officer Navy uniform in the hospital, after his release from being shot, you will notice the belt buckle is centered incorrectly. A for effort, F for wrong way. Any military uniform, the belt buckle is centered off of the zipper flap - to the left, but in the movie it is centered off to the right. Another military uniform mistake. Someday these movie makers will get it right.
Visible crew/equipment: When Shane and the kids are going home you can see a camera's shadow on the van.
Answer: No, it is just his sock.
It's a cast with a sock over it. Since the movie is shot out of sequence, possibly he might have hurt it during production.