The Yankees announced that X-rays were negative.
Nova left after fielding a high-hopping ground ball off the bat of Orioles infielder Wilson Betemit in the sixth inning.
Three innings earlier, Nova had taken a hard smash off the bat of Nick Markakis off his right ankle, but remained in the game despite hobbling around for a while after the play.
It was unclear whether the second injury was related to the first, but it was obvious that Nova was in pain as he came down after snagging Betemit's ball and flipping to first baseman Mark Teixeira to complete the out at first.
Manager Joe Girardi and a team trainer went out to the mound to examine Nova, who was removed from the game and replaced by left-hander Clay Rapada. Nova walked from the field without assistance but appeared to be limping slightly.
Nova allowed seven hits, including a long home run by J.J. Hardy, and five earned runs in 5 1/3 innings, but left with the game tied, 5-5.