After passenger loading had been completed but before the engines were started, the pilot remembered that a nosewheel chock was still in place. She disembarked and removed the chock, however the aircraft commenced to roll down the slightly sloping tarmac area. The chock was replaced but the aircraft rolled over the chock and the left mainwheel passed over the pilot's right leg. The aircraft came to a halt at the bottom of the slope. The pilot was subsequently unable to recall whether the parking brake had been fully applied, or whether she had inadvertently released the brake when pushing her seat back with her feet on the rudder/brake pedals prior to disembarking to remove the chock.
