Employee pulling on ratchet, the socket slipped off bolt, he fell on his back side. When he landed, he braced himself with right hand. He felt no pain or strain at that time but felt it later that evening. On 6/3/2014 employer was notified EE had MRI and the results deemed by physician on 6/2/2014 to be work related injury as a result from first aid occurring on 3/17/2014.