Chalmers was ejected with 5:01 left in Miami's 110-104 victory after throwing a forearm that hit Nowitzki's head.
It was Chalmer's second flagrant foul in nine days. He earned one and was fined $15,000 for fouling
Los Angeles Clippers forward
Blake Griffin on Nov. 7. Chalmers is appealing the fine.
With another flagrant, Chalmers could be facing an automatic suspension. The NBA uses a points system to determine the severity of flagrant fouls. Both of Chalmers fouls were ruled flagrant 2, worth 2 points each. By rule, a player gets suspended for the next game once he exceeds five points.
Following Friday night's game, Chalmers said he was pushed into Nowitzki by Mavericks center Samuel Dalembert.
"Dalembert had my arm so I had to get my arm free," Chalmers said. "There was nothing intentional about it. I didn't even see Dirk."
The guard tried to explain to the referees before being ushered from the court by Heat security.
"I just told them, 'Look at the replay and look at Dalembert holding my arm,'" Chalmers said. "That's all I said to them."
A Flagrant 1 foul is "unnecessary contact committed by a player against an opponent. The opposing team is awarded two free throws and possession."
A Flagrant 2 foul is "unnecessary and excessive contact committed by a player against an opponent. The opposing team is awarded two free throws and possession and the player committing the foul is automatically ejected."