Garza was struck by Jeff Francoeur's liner with one out in the second inning against Kansas City.
"I've got a lot of tattoos over there," Garza said. "It's nothing really. It hit the lower lat under my rib. After I took a deep breath, it didn't hurt."
After manager Mike Quade and a trainer came out to check on him, Garza retired the next two batters. He was then removed for precautionary reasons.
Garza is in his first season with the Cubs after being acquired in a trade with Tampa Bay.
Bruce Levine and the Associated Press contributed to this report.