Last night I wanted to change the cartridge for my kitchen faucet. I was able to close the oval shape knob for the cold water. The hot water one would not move. I tried removing the center screw and tapping it to loosen it. Neither helped and it won't turn to shut it off. My main water shut off valve is also messed up and I dont want to touch that to fix this. What can I do to get the hot water valve to turn and shut off? It's a full turn valve.