Brief Answer:
detailed below.

Detailed Answer:
Hello,

Welcome to Healthcare Magic.

I read carefully your query and evaluated the picture you provided.

There are 2 possible causes:
-It might be a fungal infection
-It might be genital herpes.
If the lesion start without previous symptoms (like pain and itching 1-2 days before the rash)it is indicative for a fungal infection.
I would suggest to keep the area clean.
Apply Clotrimazole twice a day for some days.If it seem to help ,continue with the antifungal cream until the lesion heals.
If you have had a possible exposure to herpes lately or you have had a herpes before and the antifungal cream doesn't seem to help ,then it is possible to be genital herpes.In this case it will go on it's own for 1-2 weeks and no treatment is needed.
Avoid sexual intercourse until the rash heals.

Hope it helps.
Let me know if you have any other questions.

Kind regards,
Dr.Rovena Murati

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Brief Answer:
detailed below.

Detailed Answer:
Hello ,

I apologize for the delay in answering your query.

It is not very characteristic for genital herpes to show one day after a possible infection.At least it takes 3-5 days after the exposure (it may take up to several months).
A fungal infection may cause symptoms after 2-5 days after infection but it is not always related to sexual intercourse ,which means that although you can catch a fungal infection through sex (if your partner has a fungal infection) but this is not a sexually transmitted disease.
The genital area is very prone to fungal infection because of the moisture of the skin.So you can develop a fungal infection on your own (not a transmitted infection).
A genital herpes is a sexually transmitted disease.This means that someone should transmit you the virus is order to develop the infection.

In your case is most likely to be a fungal infection.I would suggest to start the antifungal cream and see if the rash will improve.

Take care.
Dr.Rovena

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