I would recommend you to show to a orthopaedic surgeon
and get your self examined. I do not thin it can be a very serious problem and most probably it is a coccydynia
. That is inflammation near our tail bone. Do you have difficulty in sitting on hard chair. I have following advice for you.
1. Avoid any more splits
2. Sit in a tub filled with gentle warm water twice daily for one week
3. Take muscle relaxant
like Myoril for pain relief.