Haha sorry. Just seeing a black dot on my testicle freaked me out
Patience, patience. It's the weekend, and nobody is on standby to answer questions 24/7.
For at least 3 reasons, you can be sure this isn't an STD and probably not related in any way to the recent sexual exposure. First, no STD causes such a symptom. Second, the location is wrong -- if the oral contact was with your condom-covered penis, nothing would first appear on the scrotum. Finally, 2 days is really too soon for any STD to show up.
Of course see a doctor if you remain concerned about it.
but let me clarify, put a condom on for intercourse.