An aggravated piercing can create a blood- or pus-filled growth that is painful to the touch and does not respond to regular cleaning. If the infection hasn't become chronic, then it is easy to remedy.
To treat an infected growth, cleanse the area two or three times a day and apply one or two sea salt soaks per day. Use mild antimicrobial soap because this increases the chances of healing the infection without causing more agitation. The sea salt soak draws out the pus and blood, easing the pressure and aiding healing. If the growth does not clear up within a few days, consult a doctor.
Sebaceous cysts require treatment from a doctor if they do not clear up on their own. These are generally painless unless they rupture or get infected. Sebaceous cysts are easy for doctors to diagnose and treat. Do not attempt to squeeze or puncture them at home; the best thing to do for sebaceous cysts is to get medical treatment.
Keloids are also sometimes caused by piercings. These are a formation of scar tissue caused by the body attempting to over-defend itself. For the most part, keloids must be removed surgically, explains About.com. If the bump hurts or oozes anything, then it is not a keloid and may be treated as an infection.