Welcome to the forum. The direct answer to your question as posted in the title is no: it is not possible for symptoms of any STD (or any other infection) to begin so quickly.
Now having hread the question itself, I will elaborate. The minimum interval for symptoms of STD is probably 24-36 hours, and even that would be rare and applies only to a few infections, such as gonorrhea -- and even that usually has a 2-5 days incubation period. For herpes, the incubation period can also be short, e.g. 2-5 days, but often is longer; and the interval is longer still for most other STDs, e.g. 1-2 weeks for chlamydia, 3-4 weeks for syphilis.
In any case, really are at little or no risk anyway. Such fleeting, brief penetration or brief penile-vaginal contact is unlikely to result in any STD. Your symptoms are typical for genitally focused anxiety -- i.e. an emotional reaction to the sexual exposure, which you obviously regret. My advice is to try to stop worrying about it, and I see no need for testing. Of course if you develop more typical symptoms -- visible open sores or discharge of pus or mucus from your penis -- you'll need to be examined and tested. But I don't expect it to happen.
I hope this helps. Best wishes and happy new year-- HHH, MD
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As I said above, "you weren't at risk of catching anything". Therefore, it is sure you didn't catch herpes, and your own doctor has confirmed you don't have it. And I agree that your symptoms have no rational explanation except anxiety. Neither herpes nor any other infection can cause "on and off" sensations like the ones you describe.
Follow up: (Apologies if I need to ask another question for a response, I will be glad to do so, if need be.)
I went to get tested as the strange tingling sensation continued for days on end. The physician also claimed there was nothing to worry about and that my penis looks healthy and didn't see a need for herpes testing.
Considering the professional advice of yourself and the physician at the clinic, it is safe to assume I do not have herpes? The tingling sensation has been on and off since literally twenty minutes after the sexual encounter til now. I'm pretty sure this is anxiety spurred on by the fact that a blood test for herpes would not show a positive for several months.
Since you weren't at risk of catching anything, of course you can safely continue unprotected sex with your regular partner(s). Given the nature of the exposure, this would not be in the least bit irresponsible.
If despite this advice you decide to be tested for STDs, then have a urine test for gonorrhea and chlamydia any time more than 3-4 days after the exposure, and blood tests for syphilis and HIV at 6 weeks.
Thank you for your hasty response!
I suppose my only remaining question is whether I can return to sexual activity? I do regret doing what I did and I have suffered from anxiety disorder in the past, so it's not a huge surprise. I just don't want to be irresponsible.
Having dealt with anxiety in the past, I can certainly apply those techniques to move past this. I just don't want to run the risk of infecting someone I care about with something I may/may not have. I agree that I likely do not need testing, but in the event that it becomes necessary, how long after would be an appropriate time?