Ok so the best thaing to do is have it looked at buy a dr. Olney a dr can tell what it is
now any sore that comes in contact with urine will be painful and any sore will be red swollen itchy after coming in to contact with urien. I know herpes is the first place your mind wants to go when you have any sore that you dont know where it came from.
Forming a timeline is alaways good. Like when was your last sexual incounter. How many days has it ben. Did you have burning itching tingling in that spot befor the spot appeared.
How long have you had it? Are there any other symptoms, like painful swelling in your groin? Vaginal discahrge? Fever or headache? Has this happened before? If so, how often? Presumably you're sexually active, right? Have you had a new partner recently? Or a partner with any known health problems?
You need to get this checked by a doctor or clinic right away, today if possible and for sure within a day or two. It could be herpes, which is the most common cause of new genital ulcers (open sores). The sooner you are seen, the more accurate the diagnosis will be. You probably should have a specimen collected directly from the sore to check for the herpes virus.
In the meantime, fill in the missing information which will help tell whether or not herpes is likely.