JUST AS THE AIRCRAFT WAS BEING STOPPED ON CONCOURSE 'C' TO DEPLANE PASSENGERS, A GROUND EMPLOYEE WALKED BEHIND THE #2 ENGINE TO CHOCK THE RIGHT MAIN GEAR. AS HE WENT BEHIND THE ENGINE, THE JET BLAST (EXHAUST) HURLED HIM ABOUT FIVE FEET TO THE GROUND. THE EMPLOYEE SUSTAINED A BROKEN JAW AND SEVERAL BRUISES AND LACERATIONS. HE HAD BEEN HIRED ON 6/9/89 (17 DAYS BEFORE THE ACDNT). ACCORDING TO HIS TRAINING RECORD, HE HAD RECEIVED TRAINING IN RAMP SAFETY.