Justin Bieber may have turned over a new leaf, but not everyone got the memo ... because TMZ has learned a guy filed a police report ... claiming he was decked by security just for snapping a pic.
Steven Prince tells TMZ he was at FLUXX, a San Diego nightclub, Sunday to watch T.I. perform. He spotted Bieber in a VIP area and went over to take a photo.
Prince claims a security guard screamed at him and began shoving him, then punched him twice in the face -- on the cheek and jaw.
The guy claims the club tried to make nice by offering him a free drink, but then kicked him out.
Prince filed a police report and -- surprise -- he's lawyered up and plans to sue.
Sources close to Bieber claim there was an incident but insist the security guard did NOT work for Bieber ... he was hired by the club.