Hello and thank you for the question.
Answers given are for informational purposes only and are not meant to replace an exam by an in-person.
I am Dr. Sohaib, a practicing Internal Medicine Specialist and i will do my best to help you today.
Extremely unlikely to be herpes.
Also whenever you put hydrogen peroxide on any open sore or an ulcer or an area where there is breech in skin, the surface will turn white because hydrogen peroxide is base chemically and it will slough out the necrotic or dead tissue/cells from any surface.
You should not put this again over the surface, rather use a topical antibiotic ointment such as Bacitracin and monitor this closely over next few days. This can be due to un-noticed trauma during sexual intercourse or friction rub from garments.
However, you can not absolutely rule out herpes at this point, because one can have herpes even if he/she does not have any lesions, so to be absolutely sure about this, you need to get tested for herpes.
I would have been worried too if I were at your place, but let me reassure you that this is a treatable condition and carries a good prognosis with appropriate management.
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