I am an 18 year old male and have had a bump of the base of my spinal chord, just below my pants. Has been there for a while (6+ months), but for the last few days, has been hurting badly when I touch it and even a little uncomfortable when I sit. The size of the bump is not very big, though it is big and stiff enough to know that it is not inside my body (it is above the surface of my body). What could this be? Thank you for the help.