We don't currently have specifics about this but it sounds like AJ Styles may have suffered an injury of some sort during last night's Royal Rumble match. As you can see in the video below, Styles took a Spear from Edge and sold the move by rotating in the air. However, the landing was not a smooth one as he appeared to take the bump directly on his left shoulder.
Styles was seen being checked by trainers by ringside and it's said that he was helped by them backstage as well.
If you take a close look at the match, you may notice that Styles seemed to stop his fellow Superstars from touching him and then appeared to call an audible by having Edge eliminate him sooner than planned. That would explain why he didn't make a huge impact in the bout and we'll hopefully have an update soon.
However, with WrestleMania fast approaching, an injury couldn't come at a worse time for the Phenomenal One...