I healed my tailbone pain (or was it pain of the disk between the tailbone and spine) with McKenzie method, but this exercize is also popular in many systems of stretching. You lie on your belly, place your palms on the floor or bed at the level of your head, and you rise your body using your hands. You will feel lower back area straightening. You can adjust your hands to reach painful spot precisely.
If it's too strong for you, start lightly. After some practice you can add one move to strenghten this - when you are in upmost position, breath air out of your stomach and lungs.
Do it 10 times every 2 hours for 2 weeks, than allow some time for regeneration.