hi, thank you for providing the brief history of you. A thorough clinical musculoskeletal assessment is advised. As you have problem getting up from a chair and sitting down, also you have directly hit the tail bone from a fall, I suspect it to be a lumbosacral spine issue. Taking an X-ray or an MRI should help the understanding better. Since MRI will reveal the soft tissues and also the bony regions which will allow a better understanding and a safety measure for future pain and aches. There might be a disc injury or may be a bony fracture which is not noticed yet. Post MRI we can figure out one. The choice of treatment is normal, physical therapy. With therapeutic ultrasound therapy and TENS therapy the inflammation and pain can be reduces. Post which exercises will be planned to regain the muscle strength and also the stability of the lumbosacral joints. In my clinical practice such cases comes with listhesis and with the help of physical therapy they respond well. Regards. Jay Indravadan Patel