How do i fix my main water shut off valve?

Someone turned my main water shut off valve off while i was gone. When they did this they snapped the metal that stops the valve from going too far in one direction. Now when I turned the valve back on Water pours out of the adjacent faucet even when the faucet is tightly off. It does not leak out of valve, but comes out of the faucet. Any ideas of how to fix this?