Im changing my brakes pads today and notice that some brake fluid was over-flowing back up to the brake fluid container in the engine bay as i was depressing the pistons back to insert my new pads. well, i then twist open the cap on the brake fluid container and re-tighten it back up. I go back to de-press the last piston and now it wont budge. its half out and wont go back in as hard as i try. Any suggestions?