The wiring to that light could be bad and also could be a bad fuse/switch. Also the bulb could be burned out. I would check the power to the switch and see if there is power going to but not leaving it. If that is the case it is a bad switch.
IT sounds like you have a problem in the electrical system. Either the left light is blown, the wires are damaged, or the switch is going bad. Check each one until you pinpoint the problem.
This is very simple. Your bulb is more than likely out. Go to a parts store and have them look up your car. They can tell you which bulb you need to replace. This is very easy.
One possibility could be that you have a burned out bulb. They can be purchased at any auto parts store. If that doesn't solve it, you could have a short in the electrical wire.
