Usually people with history of prolonged sitting have lower back related issues. The pain may not be in the tail bone because tail bone problems usually occur due to a fall on the buttocks exactly on the tail bone. This is common problem probably due to either the muscles which must be strained or the ligamentous issue in the back. Chronic pain may also suggest a disc involvement which causes impingement over the spinal cord leading to radiating pain.
Next Steps
1. pain killers - Tab. Hifenac-MR twixe daily after meals for 3-5 days
2. Antacid - Tab. omez once daily before breakfast 3-5 days
3. gentle physiotherapy for upto 3 weeks
if the pain does not subside, then you go for an MRI of the LS spine to see what the problem is.
obviously physical Consultation gives us a better idea, so I'd strongly recommend that
Health Tips
if the symptoms are increasing during physio, stop the phsyio and go for an MRI