EE stated that while bolting in the face of #5, sectional pinner steel lodged into the roof. As he turned to speak to the scoop man, he placed right hand on the boom of the bolter. The steel dislodged from the roof & fell on his right hand between the 1st & 2nd fingers near the knuckles. The steel caused a laceration that required 2 stitches to close. He was not wearing right PPE.