Hi everyone...I'm in need of some urgent advice.

I know it sounds trivial, but my rear passenger compartment dome light (interior light above the rear seats) is inoperative. I tried using the switch (both rear light and door contact), and the light would not turn on. Now, I am not sure whether the light switch is on or off. If the switch is on but the bulb is burned out, will my battery die overnight or in a parking lot? How do I prevent this?

Help!