2002 Chevy Cavalier shiftier knob wont allow the engine to shut off

I hve a 2002 Chevy Cavalier LS automatic with the shifter on the floor. The problem is in the knob (ball) of the shiftier. Something in the ball is broken and does not allow you to shut off the engine or remove the key from the ignition. Can't shut off engine, or if you can, you cannot remove key from ignition. If you play with the shifter, sometimes you can get it to release the key from the ignition.