If the pain continues, have your doc look into the possibility of arthritis. We are more prone to arthritic conditions such as
www.mayoclinic.com/health/ankylosing-spondylitis/DS00483I have Sacroiilitis (inflammation and pain in the SI joint - the joint that connects the hips to the spine) and sometimes it affects my tail bone. It hurts if I sit or lay for too long and walking or standing for an extended period of time. It especially hurts if I lie on my back or stomach but not if I'm on my sides.