Broken crankshaft sensor in engine block?

Yep, it happens, can you still see the end of the sensor? If so, I would try to drill a small hole in what is left and install a wood screw to get a bit on it and pull it out, if not you will need to remove the engine pan to push it out from the inside. Here are instructions on how to remove the oil pan in the images below. You might need to rotate the engine over to gain clearance so you can push the sensor fragment outwards. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem.