Major League Baseball initially suspended Contreras two games on Saturday along with an undisclosed fine for his actions during Friday night's game against the Cardinals.
Cubs right-hander John Lackey also was fined after both disputed a call by home plate umpire Jordan Baker during the 8-2 win over the Cardinals.
Contreras threw down his catcher's mask moments after Lackey was ejected in the fifth inning for arguing with Baker. The mask made contact with Baker's leg after Contreras was also ejected.
With two on and two outs in the top of the fifth inning and a 2-2 count on Cardinals pitcher Carlos Martinez, Lackey threw a slider that the Cubs thought was a strike.
After Lackey argued the call, he returned to the mound and his 3-2 pitch was hit into center field for a run-scoring single. Lackey then sprinted to home plate and screamed in Baker's face, getting the ejection, followed by Contreras.
Contreras apologized to Baker before Saturday's game.
"I did something wrong, and that wasn't me; that was the adrenaline from the game," Contreras said after Saturday's 4-1 win. "I needed to apologize. Nobody's perfect. That was part of my job today was to apologize to everybody and move on. "(Baker) told me, 'It's over, and we need to play the game and forget about it.'"
Cubs manager Joe Maddon told reporters Sunday that he was pleased the situation was resolved.
"It's good news," Maddon said. "We'll have the one game over with and move it on from there. Get it off his mind and play it forward."