actually know the answer. I don't think it's against any rules; the home plate umpire usually calls a time out immediately after a batter is hit by a pitch, so theoretically, the pitcher should be allowed to go check on the batter. The only thing I could think of is it's either a matter of staying clear while the trainers (if it looks really bad, sometimes trainers from both teams come out) check on the player or possibly it's a matter of sportsmanship or not giving aid and comfort to the enemy or whatnot.
I've seen batters hit by pitches before but not often in the head. I wonder if Fry would've been able to get out of the way if he hadn't already been squared around to bunt?
