I drive to work and the brake light wasn't on. After I parked and got out and when I came back to my car and started it up the brake light was on. The parking brake which is a hand brake is not engaged at all.
Are you talking about your idiot light in the dash or the actual brake lights on the back of the car? The parking brake has no electrical connections. If it's the idiot light, there is a small switch on top of the brake distribution block, it tells you there is something wrong with your brakes. If it's on, could be a bad switch or a leak. If it's the actual brake lights, there is a switch on your brake pedal arm. It could be stuck or bad.
Check the fluid level in the master cylinder. If it got to low you will need to check for leaks, repair and bleed the brake system.