EMPLOYEE STATED THAT HE WAS BACK DRAGGING THE ROAD WITH THE DOZER. HE BACKED OVER A ROCK WITH THE DOZER TRACK. AS HE DID, THE DOZER JARRED THE EMPLOYEE WITH PAIN OCCURRING IN LOWER BACK AREA RADIATING INTO GROIN AREA. WENT TO DOCTOR IN ER THAT NIGHT AND MUSSED THE NEXT SCHEDULED WORK SHIFT.