Thank you for your post. You are probably having a vertebral
column injury or spinal cord injury
or just post traumatic pain ( due to pressure on your back muscles and subsequent inflammation).
Spinal cord injury is most unlikely because if you have, you should have started developing nervous deficits on your upper or lower extremities depending on level of the lesion on your spinal cord. Cord compression due to vertebral column displacement is another possibility but as i said developing neurological deficits would have been showing as symptoms except of course the injury is very very mild and also pain will not be the most likely symptom. Vertebral column injury will simply be a small fractured bone of a vertebrae or displacement/dislocation which would present as a pain of progressive intensity as you continue daily activity. The other option is you are having back muscles contusion
that should disappear with use of analgesics like as acetaminophen
or Tramadol or anti-inflammatory like diclofenac
either orally or local pomade with massaging.
In either case, you will probably need to visit a radiologist
to run a CT scan or X-ray of the vertebral column to rule out any serious abnormally.
Hope this helps