You sure it is only the parking brake?
Is the brake pedal suddenly mushy, car doesn't stop good?
First check your brake fluid one reservoir may be empty, or near so.
It sounds like your balance valve may have moved off center, causing the brake light all the time.
If the fluid went away, find out where the leak is, hose, tubing or wheel cylinder. Ten fix the leak, fill it up. You'll have to bleed the brakes in a certain sequence to get the valve back to center...