Hi, I Have Been Having Pain Right Below The Opening

hi, I have been having pain right below the opening of my vagina on the side. it seems a little white and it's a sore, almost feels like a cut. my partner and I had intercourse on Monday, and it still hurts today. in fact I didn't feel it til 1-2 days after the intercourse. it also hurts at the very bottom below the opening but there is no sore there-only one sore. my partner has been tested for STDs and they have all been negative. I have not had intercourse before my partner and I for a while. I need to know what this is because I'm kind of freaking out!