They are formations of scar tissue that grow after trauma or
piercing of a body part
is done.
The other possibility
is of a cyst which
is formed when irritants like oil, sweat, dirt, perfume, hairspray and lots of other things can aggravate a piercing and cause an infection. It will create a growth filled with blood, puss, and or sebum but it is usually painful and may discharge pus or blood. If it is a keloid that you are having, then surgical excision is to be done.