Some wrong info above...the most common STD's from oral sex is gonorrhea and NGU and even those are low risk. Syphilis is possible and so is herpes but both of those are a lot less common then the 1st 2. Testing times is 1 week for gonorrhea...but without syptoms (discharge, burning while urinating) no real reason to test, same with NGU.
Herpes is 4 months and syphilis is 6 weeks.
HIV is not a risk with oral sex.
Receiving oral sex is extremely low risk for STDs such as HIV. You can catch Herpes, Gonorrhea and possibly Syphilis. If you want to get tested for HIV, Herpes or Syphilis you should wait 3 months. However don't let this event worry you too much. First of all this guy was probably telling the truth when he said he had no STDs. And receiving oral is not a very good way of transmitting STDs except Herpes. Good luck