Freak play in the NHL on Monday ... a puck made its way through a tiny window in the glass and hit a photog so hard in the jaw -- the dude needed a bandage to stop the bleeding.
The unlucky shot went down in the 1st period of the Capitals vs. Sabres game in Buffalo, N.Y. ... when defenseman John Carlson tried to clear a puck by sending it up the boards.
The problem ... the puck somehow made its way into the small cutout of glass where photographers place their camera lenses through -- and it caught a man right in the face.