2004 Kia Picanto back left wheel is locked

Hi, i have a problem with my 2004 1.1 lx kia picanto. The back left wheel is locked, it doesnt move, as if the hand break is pulled us. The brake pedal gets hard and the entire car doesnt move. Recently i had a mechanic instant a new rubber on the brake pedal because the original one fell off, causing the brake lights to stay on even when the engine is off. Please help