The fall on butts has hurt the distant part of your spine- called coccyx
This is diagnosed by Xray spine Lumbo sachral regeon.
It is many a times broken & can not be plastered,heals by itself,but take a period of 6-12 months for healing. The only way to manage is-
- sit on a soft surface/ Tire like air seat
- Use Nonsteroidal anti inflammatory drugs suppliment with calcium & vitamin D s to manage pain,
-Uncontrolled pain some times needs surgical removal.