The injury is a legitimate one. Styles confirmed on his Mixer account post-Raw that he's experiencing issues with the AC joint in his shoulder.
Styles said of the injury, "It's rubbing up against bone and we thought I had a fracture. It may not be the case, which is a good thing. It may require a shot to keep the swelling down."
Terming the injury to be "not major", Styles (who turns 42 on Sunday) says he will take time off to rest and properly heal, but wants to come back as soon as possible.
The former two-time WWE Champion has not wrestled since his Universal title match with Seth Rollins at Money in the Bank nine days ago. Dave Meltzer said on the post-Raw edition of Wrestling Observer Radio confirms that Styles is off of upcoming house shows.