I see nothing that indicates this being STD related and with the negative tests it backs up my 1st thought.
I read your post with Grace, you were tested for chlamydia and Gono a week after your encounter you are not infected with chlamydia or gono... also oral is not a risk for chlamydia.
You were also at risk for NGU, Syphilis and HSV... how ever oral either way receiving is a low risk encounter. the bump sounds like an in grown hair that you irritated and messed with and you pretty much explained your pants did the rest. Yes your sor on the scrotum could cause your lymph node to swell... any infection will do that.
If you are concerned of HSV then you will need testing 4 months post the exposure.
Stress can cause a lot of unwarrented symptoms, try to relax again you had a low risk exposure