For what reason does my tail bone hurt?

Probably bumped it: Stretch it out slowly. . If this doesn't resolve the problem see your primary care provider.

See below: Sounds like you have coccydynia or 'tailbone pain'. This can occur with trauma to the tail bone, abnormally positioned coccyx, or poor sitting posture. Try using a good lumbar support to help shift your pelvis forward. This will put the pressure on your ischium. (bottom part of pelvic bone), and will shift the weight off of your coccyx (tailbone).