His pain was so great Friday night he was lifted after throwing five no-hit innings against the Florida Marlins.
Nationals Manager Manny Acta noted on the team's Web site Saturday that Hill appears headed for the disabled list.
"I'm going to take it easy for a couple of days, get the MRI and see what's going on exactly and then go from there," Hill said.
For the season, Hill is 3-3 with a 2.70 ERA in eight starts.
He has walked 16 batters and struck out 33 in 50 innings.
Both men agreed Hill would miss his next scheduled start Wednesday against Atlanta.
"We're not going to rush him back," Acta said. "We're reluctant to make any type of announcement until we have the MRI."