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Lesions on your vagina can be from a number of things. If you recently had rough sex then it is very likely that is what it is from. If this is the case, I recommend "pelvic rest"-- ie, nothing in the vagina for the next couple of weeks until everything heals.
There are other possibilities as well depending on what these "cuts" look like. It is also possible that you could have herpes (hard for me to say without looking myself). If you have any worries about the possibility of this STD then you need to be seen by a doctor and have him or her swab the lesions and send it for culture to tell you for sure. If it is herpes, there is no cure but there are medications we have that can help suppress outbreaks and shorten this one (if that's what it is).
In the meantime, if it is just cuts, then I would call your doctor and ask for a topical lidocaine jelly prescription. This will basically help numb the area for you so that you can wash it, etc. Also, when you pee-- if the urine (which is acidic) touches the cuts it will burn. What people can do to help relieve this is use a spray bottle as you pee to dilute the urine and make it less acidic when it touches those areas (we often do this for women after vaginal delivery
with cuts). You may also find relief in "sitz" baths-- basically a warm soak (with epsom salts if you like) that you just soak your bottom in. Additionally, the vagina typically heals very quickly and I imagine this will be cleared up in the next three days or so. You can also try ice packs on the area as well if the pain is really bad.
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