He said it happened on the third-down catch he made with 8 minutes left in the game on Sunday, a throw where he dove back to catch it just short of the first-down marker.
He stayed in the game and made two more catches on the final drive. He'll have x-rays later.
Also, check out former Newsday legend Paul (Dr. Z) Zimmermann's piece off the Super Bowl, with some quotes from Giants team doc Russ Warren:
"Guys doubling over, cramping, I didn't think some of them would make it," New York's team doctor said after Super Bowl XLII on Sunday. "Plaxico Burress, my God, what pain he played in. He fell in the shower on Tuesday. I thought he'd torn his MCL. You didn't know that, did you? Of course you didn't. No one knew. And he'd injured his knee in the Green Bay game.
"He said, ‘Shoot me up for this one if you have to. I'm not going to miss the Super Bowl.' "
I should also mention that Dave Diehl played almost the entire season with a torn ligament in his thumb.