fuses,When I put my foot on the brake my back left brake light goes off, when I take it off the brake the brake light comes on

I have a Toyota Corsa 1992 model. Im based in NZ. My friend slammed my boot shut extremely hard which appears to have damaged the brake lights. A yellow "check lights" symbol now appears on the dash. Subsequently when I put my foot on the brake my back left brake light goes off, when I take it off the brake the brake light comes on so the opposite of what should be happening. The problem is only on the left side and applies only to the brake light. Help me please
My car has a manual transmission.