Vagina Blister?? has anyone had this?

TMI: Okay so one day I was in the shower and I felt a tiny sting as the water hit, when I looked down at my private area I saw big bump on my outer lip. It was red, and had a white head, when I pressed it, it popped so quickly with clear fluid and it started bleeding. It was a single bump, and it didn't hurt at all. Didn't even notice it until I went in the shower and felt it. After that it was bleeding alot, and it was a little pain just in that area. I freaked out and went to the doctor because I thought it was a blister, and thought it could be herpes but the doctor said herpes come as multiple blisters that are painful, and you can't use the restroom so it couldn't be that. But I'm still trying to figure out what that was.. has any women had this watery bump as well? I didn't have pain urinating, wiping, walking, sitting or anything. It was only sore when I touched it. And the crazy part is, it didn't even leave a sore or scab over. It was gone in days. I'm just confused, I haven't even had sex in months when this happened.