He left the arena without crutches or any help and was in good spirits after the game; even said he doesn't expect to miss any time. Very possible that this is similar to the Pierce injury in 2008 where it looked a lot worse at the time than it actually was.
Exact same thing happened to Bradley Beal earlier this year; looked like he tore a ligament and had to be helped off the court, then he was ruled fine for the next game.