Hi, thanks for writing to HCM.
From the description, I feel that you are suffering from Coccydynia
(tail bone pain
The hard mass you are feeling could be cyst or a tumour. An xray of the coccyx and MRI scan is needed to establish the correct diagnosis.
The general treatment guidelines for this condition are -
* Sit completely upright with proper posture — keeping your back firmly against the chair, knees level with your hips, feet flat on the floor and shoulders relaxed
* Lean forward while sitting down
* Sit on a doughnut-shaped pillow or wedge (V-shaped) cushion
* Apply heat or ice to the affected area
involving strengthening of pelvic area muscles , stimulation with ultrasound
* Take over-the-counter pain relievers, such as acetaminophen
(Tylenol), ibuprofen (Advil)
If your symptoms are not relieving with the above measures, consult an orthopedic surgeon for further management.
Hope this information is helpful. Good day