What Causes Lump In The Labia Minora?

Hi , I got a lump on my left labia majora. initially it was very small later it became little bigger. and noe it is painful and little hard too and it is red in color. i am taking Ampoxin -500 antibiotic. and i have two pain killers , dolokind plus and moxikind-cv 625. can u please seggest which pain killer i should take. I do take pain killers very rarerly.