Thanks for writing to us.
The lump you have on your tailbone could be a pilonidal cyst
It is common for young men and the peak incidence of Pilonidal disease is between 16 and 26.A Pilonidal cyst may remain harmless.
If it becomes infected, however, it will cause pain, inflammation and usually drainage
So I would suggest getting this evaluated by a doctor for an accurate diagnosis and appropriate management.
Wishing you good health...
Dr Saurabh Gupta.