Sebaceous cysts are common noncancerous fluid filled lumps found just underneath the skin. They don’t usually hurt but may become red, tender and sore if infected. Skin cysts my progress to become a boil or abscess which are infected and contain painful collections of pus.
A typical skin cysts is a round dome-shaped firm lump, yellow or white in colour often with a small dark plug which may erupt from time to time. They vary in size and can be smaller than a pea to the size of a grape or even a small plum.