The distribution block has a sensor that identifies an inbalance in pressure. In your case caused by the line lock. You need to recenter the sensor. Using a set up like you would for bleeding the brakes, open one of the bleeders, gently press on the brake pedal until the light goes out then tighten the bleeder. I would guess that you need to do this on the rear. If doing this on the rear does not cause the light to go out, then repeat on a front brake bleeder. Don't forget to check the fluid pressure afterward.