This may be pilonidal sinus, abscess or lipoma.
Conditions needs evaluation with X-rays or MRI.
You can try:
1. Sitz Bath thrice daily for 1 week.
2. Spine extension exercises.
3. Rest for 5 days .
4. Medications like Ceftum, Etova MR, Enzomac and Neurokind LC will help.
Next Steps
Get the swelling evaluated by a general/Orthopaedic surgeon.
Health Tips
Do not worry.