Red Bumps Outside Vagina Lip

I have just recently got off of the Nuva Ring (birth control), to be more precise it has been a little bit over a month since I've been off of the ring. I had my period 2 times in one month because of it and I was still able to recieve my period the following month, but after my period was over I had this strange red bump on the lower part of the outer lip of the vagina. The bump is at the very, very bottom of the lower lip where it is the smallest. I'm not positive when the bump first came about because I figured it was a ingrown hair or a pimple that would go away so I didn't pay too close attention to it. But this bump has been there now for a while perhaps 2+ weeks, and some days the bump is normal where it's small and looks as if it is going to disappear but then it grows and then shrienks. It might be because I touch it and then i stop touching it; when I don't touch the bump it doesn't hurt but when I do it is sensitive, it is not itchy, and it is red. It was smaller just yesterday but then I tried to hurry the process of its disappearance so I wanted to pop it but instead of it staying its size it grew bigger. The bump seems inflammed and irritated.

I know it is not an STD because I had a pap smear about a couple days to a week before it showed up and I tested negative for everything, so i know it isn't from an STD.

Is it a pimple that has become infected or is it something worse or is it just a pimple that i need to be patient about that it'll go away? I also don't understand what it is and if something is wrong with me I need to know. Any information will go a long way and help me greatly. Please any suggestions will be great because I really want it to go away and have my mind at ease....