Operator tramming track dozer 26641, encountered a rock caused operator to inadvertently set park brake. Machine suddenly stopped, operators left shoulder jammed causing a shoulder strain. Employee was given a work as tolerated release 1/2/2020, then on 1/9/2020 notified the mine that the MRI showed rotator cuff tear, taken off work 1/9/2020. Begin physical therapy 1/13/2020.