Welcome back to the forum.
Based on this question and your other one on this forum last September, it seems you have mistaken ideas about STD risks. The STDs are difficult to transmit -- in fact, that's why they are STDs in the first place, i.e. without true sex (unprotected intercourse) there is little or no risk. Oral sex is low risk even without condoms (and zero risk for some STDs), and is certainly no significant risk given the very brief, fleeting exposures of the sort you describe here. Analingus carries little known STD risk, but is high risk for gastrointestinal infections. You are not at risk for any STD, including herpes, HIV, HPV, etc.
And as your doctor said, your sore throat is nothing to worry about. STDs rarely cause sore throat anyway; for example, most oral gonorrhea and all oral chlamydis are entirely without symptoms. I'm sure you have a minor cold, allergy, or any of the other common causes of sore throat; your symptoms have absolutely nothing to do with the no-risk sexual encounters described above.
Please spend some time studying real STD risks. The bottom line is that if you don't have unprotected vaginal or anal sex, you are at very low risk for any STD. You don't need testing, and if you have a regular partner, you can safely continue your normal sexual practices without putting that person at risk.
Best wishes-- HHH, MD
Thanks Doc.
You've been clear as usual.
As I supposed I wasn't at risk.
I have just worried a bit due to the coincidece between my encounter and my sore throat (despite I repeated myself it started too early after the encounter).