Welcome at HCM.
I have read complete details of your question.
It looks that you had trauma & you are having pain at lower part of your back.
If it is coccyx
then it is coccydynia
.It is pain at the lowest part where spine ends.
Pain at this part is slow to go.
You should do following to have relief in this-
-Avoid sitting on hard surfaces.
-Avoid straining at stool or defecation.
-Take warm sitz bath or sit in tub of warm water in morning.
-Take a good analgesic
or aleeve for relief from pain.
Hope this all will help you.
With best wishes.