What is this?

First off, it's definitely not an STD. My fiancé barely has time to spend with me after his 12 hour shifts, let alone cheating on me. We've both only ever been with each other so there's no way he could have passed on an STD from a previous relationship either. It's to the left between my vagina and crease of my hip, hard, and feels about the size of two marbles put together although that's probably from me irritating it because it definitely wasn't that big when I first checked. I popped it and all that came out is clear liquid. Should I make an appointment or is this just an irritated gland of some sort or something else that will go away on it's own? Please excuse the hair, I haven't had the time to shave recently.