X-rays taken at the Staples Center were negative, but Carter emerged from the training room on crutches. He said he heard a "pop" in the top of his foot inside, pointing along the inside of his big toe.
Dallas trailed 73-70 with 3.1 seconds to go when Carter got the ball at the top of the arc guarded. Carter said he tried to step right to create space for the shot when he felt the pop. He still got the shot off, but it missed.
"I stepped wrong and it popped," Carter said after scoring six points in 18 minutes. "It's not broken, but it's swollen."
Carter said he will be re-evaluated Tuesday and that it's possible he could return to Dallas. The Mavs are one game into a four-game, six-night road trip. They play the Clippers on Wednesday.
The 14th-year swingman had emerged as a top reserve in his first season with Dallas. Entering Monday's game he was averaging 9.8 points in 21.7 minutes and shooting a team-best 46.9 percent from 3-point range.
In his two previous games, Carter scored matching season-highs of 16 points on a combined 13-of-18 shooting from the floor and 5-of-6 from beyond the arc.
"It would be tough, he's kind of instant offense off the bench," Dirk Nowitzki said. "We were posting him some, we were running some high screen-and-rolls, he's a good shooter to spread the floor for us, so that would definitely, definitely hurt us. But, I think this team is deep enough."
If Carter is sidelined, it would likely mean third-year guard Rodrigue Beaubois, on the fringe of the rotation with a healthy roster, would take on an increased role as he did when Jason Kidd missed four games recently.
With a full roster Monday in L.A., Beaubois did not play.
Jeff Caplan covers the Mavericks for ESPNDallas.com.