Sore vaginal entrance (left side)

The inside of my vagina, pretty much right near the opening (only on the left side) has been sore for a few days, I think it's from rough sex but it isn't going away & I guess that's because it's not having time to heal as I'm still having sex.

Has anyone had this before? I used a mirror to have a look but I can't see any noticeable tare or anything, I am still able to have good sex but it does hurt every now & then!

Burning sensation - could it be something else? Should I worry?