While Chief Mechanic and Senior Mechanic were working on fixing the kicker cylinder on the trough of pipe-cat, after facing difficulties to install the cylinder pin manually.Chief Mechanic decided to extend the cylinder hydraulically while senior mechanic was holding the cylinder using prybar aligning the cylinder piston with kicker arm (to avoid the cylinder from swinging down), suddenly the cylinder retracted, and senior mechanic fingers trapped between the bar and pipe-cat trough. (left hand ring finger and right-hand index finger). First aid was administered to IP by rig medic and then referred to PAC clinic and later to Salalah Hospital