How to remove one of the internal screws missing its head?

While screwing the system back together, one of the screw heads completely snapped off, leaving its post stuck inside the system. I've tried searching everywhere for advice on how to remove it, but I can only find information on how to remove stripped screws that still have the head attached.

When reassembled, the system now feels a little loose and makes a creaking noise when holding it, since it's unable to be fully screwed back in. Broken screw is shown on the right, left is still intact.