Haul truck driver was dumping load, when the bed lowered unexpectedly, jarring him. He was seen by an 1st responder and continued to work. 5/31 he requested medical attention, after time in ER, was sent home, referred to PCP, started days off. Did not see PCP until 6/5, released for 6/6, worked full shift, SDO 6/7 called off 6/8, currently ongoing.