What Causes Hard Lump With Discharge On Inner Thigh?

Hi, I had a small hard lump on my inner thigh for about a week, then it started to get pretty sore and the skin around it turned kindof a purple colour? I put heat on it, thinking it was just an ingrown hair or something then I sort of swelled up like it had liquid in it? It popped today but not puss or blood just a clear liquid, no smell or anything? It drains a but if I apply gentle pressure but the harder lump is still there, its abit smaller that a marble? What is it?