What To Do For The Small Mole Growing Beside The Belly Button That Is Filled With Pus ?

Doctor, i developed a small mole beside my belly button some 5 years ago and it was totally harmless for me and quite small in size. It increased in size (inside the skin) but outside the skin it grew marginally. It was of greenish/greyish color - Couple of days back, its surface got scratached somehow and yellowish thick puss came out of it. I squeezed it as far as i could - it flattened utlimately. Now after two days it has again got some puss inside - the smell of puss is extremly foul - what do you see can be it? any suggestions please?