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I have gone through your query and pictures in detail. The additional photo was very helpful. The small area that you mention is a fissure(cut). It does NOT seem to be any STI including genital herpes. It seems to be due to friction as a result of vigorous washing and rubbing.
After an exposure such as yours, I understand that you have fears of getting an STI but let me assure that you do not have any symptom indicating it. The tingling and discomfort is due to anxiety. I have seen this symptom in almost all patients fearing an STI but none have tested positive so far. Since your tests are also negative, you should relax.
I would recommend application of mupirocin cream(requires prescription) mixed with hydrocortisone cream, to be applied on the affected area twice a day for five days.
In case it doesn't resolve with treatment it would be best to visit your doctor to let him have a look.
As for statistics of genital herpes, there is a risk of transmission of about 50 % if your partner was infected. The risk is lower without active lesions. However in your case, it is unlikely you have it.
Please let me know if you have any queries.