The EE was replacing drive belts on the sand screw. He was standing at the end of the screw when he reached down to unscrew the bolt on a guard. He felt a pop on the left side of his rib cage. He reported it, but did not feel the need to go to the doctor until 8/13. He received a shot for pain on 8/13, and another for inflammation on 8/17. Released to full duty on 8/20.