I got injured at work and fell off a platform a few feet onto a metal rail, it left a red line across my tailbone and later that night I could barley sit, stand, bend or walk without being in a ton of pain.. Went to the er and had x rays done.. Nothing was found, a week later and sitting/standing still hurts pretty bad and just noticed a hard knot on the left side of my tail bone and is painful to touch. Any idea what it could be or why it s there