Pus Filled Bump Near Vagina. Using Cefilexin. Why Is It Recurring?

I have a hard puss filled bump on my inner thigh close to my vagina . When it started about a month ago it was like a pimple , i popped it and it kind of stayed open like the start of a staff infection ( i had one before). I went to the doctor and was told that it was not staff, to keep it clean and was given a antibiotic ( cefilexin). I left out of town anthed fogot to pick up the medicine but the bump had closed and seemed to have healed up so i never picked up the medicine. Now its been about two weeks and the bump is growing and is about an inch wide and alittle sore but not opened. I just went in to get the antibiotic. My question is, do u have any idea what this could be, and is it to late to take the meds to clear this, its very difficult for me to keep going to the doctor, plz give me any advise u have