Chicago starter Reynaldo Lopez hit Dozier as he was leading off the second inning. Dozier was attended to by Washington's athletic trainer. Dozier remained in the game but was removed after three innings.
"He's got a nice contusion right now so I'm assuming he's going to be stiff," manager Dave Martinez said. "Hopefully he'll be ready to go tomorrow."
Howie Kendrick replaced Dozier at second base and led off the fourth inning with a home run in his first plate appearance.
Dozier is hitting .223 with eight homers and 19 RBIs in his first season with the Nationals.
The Associated Press contributed to this report.