Lewis said the injury is "just a sprain." He was limping in the locker room after undergoing postgame X-rays.
"They said the X-rays looked good," Lewis said. "I should be fine. That's a great sign."
With rookie EJ Manuel sidelined for several weeks with a knee injury, Lewis started in his place on Sunday, completing 19-of-32 passes for 216 yards, two touchdowns and no interceptions.
Lewis' first pass of the game was a 47-yard completion to receiver T.J. Graham, the longest play of the Bills' season. Lewis later ran for a 3-yard touchdown on the opening drive.
Lewis said he did not know when he was injured.
"I just got sore throughout the game," Lewis said.