Contract miner was using a two inch wash down hose. The miner used a worm gear hose clamp to connect a fire hose type nozzle for wash down. After inserting the spray nozzle and tightening the hose clamp, miner pressurized the hose. After pressurization, the spray nozzle came out of the hose and the hose clamp retracted into his hand causing a minor cut and two stitches.