The left-hander said similar episodes in past Spring Trainings have "come and gone" and last "three days max."
Manager Don Mattingly said the club is not concerned with Ryu falling behind schedule as long as he has no setbacks.
Ryu came to Arizona in January to work out early with Korean team LG in hopes of avoiding shoulder fatigue that plagued him last year, but he dismissed the notion that the injury was the result of fatigue.
"Just part of all the conditioning," he said.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.