Have Cat Questions? Ask a Cat Vet Online.
I am so sorry Toonces got hurt...poor baby.
From your description and the negative xrays, it sounds like disc or vertebra injury.Or a sprained tail. That will heal with rest However an anti-inflammatory medication can speed up the process.
Ask the vet for a fentanyl patch which will supply constant pain medication and he will not need to take oral pain meds.
Please let me know how your boy is doing.
Best wishes and prayers for a speedy recovery.