Was told this was a lipoma three years ago - suddenly overnight it is protruding from my thigh, tender. (Photos)

I've had this lump on my upper inner thigh near my pelvis for 4 years. Went to a general surgeon 3 years ago & he said it was a lipoma - at that time it could only be felt under the skin, there was no protrusion & a very faint bruising and a tiny greyish dimple about an inch from the lump. In July, it developed a pimple on top & the pimple kept bursting open, leaking pus and a little blood. Today, it is suddenly protruding from my thigh & looks like it would burst easily, like a blister.