Thanks for writing your query
Based on your description this injury
is called coccygodynia. The lump or swelling usually subside with following treatment and it does not looks to be pilonidal cyst/sinus-
1. Sitz’s bath- sit in the tub filled with lukewarm water for 10-15 minutes two times daily.
2. Avoid sitting on hard surface and try to sit on one buttock. Avoid jerky rides and take rest.
3. Medication wise you may take Ibuprofen
for few days.
It usually takes 2-3 week time to heal. If the problem persists see your local doctor.
Take care and wish you good health.
Dr.chugh Orthopaedic surgeon