James fell to the floor on his hands and knees, then writhed on the hardwood on his stomach for a while as blood dripped from his face.
James, who had 33 points before the play, was taken out of the game with just under six minutes remaining.
The Heat superstar did not talk to the media after the game but, according to information provided during the Turner Sports broadcast, he passed a concussion test. He is expected to have an X-ray on his nose.
Despite the injury, James appeared to be in good spirits after the incident. He joked on Twitter that he might have to wear a mask similar to that worn by Bane, the villain in the Batman movie "The Dark Knight Rises."