The OP just got delayed by NICS, that's all. It just means that the FBI couldn't figure out right away if he was OK to own a firearm and they need extra time to figure it out. By federal law, if you're delayed by NICS then the dealer can release the firearm to the buyer after three business days. Usually the FBI will call back before that to give a "proceed", sometimes they'll call back with a denial, but if they don't call back before three business days then the dealer can release the firearm legally; that said, some dealers will hold the firearm until they receive a response from NICS.
Getting delayed is completely normal. Sometimes it's because you weren't born in the US, sometimes it's because you have something in your background, sometimes it's because your name is similar to a known criminal and you didn't put your SSN on the 4473, sometimes it's because NICS is extremely busy, and sometimes it's because the NICS examiner is in a hurry to go to lunch and can't be bothered to actually do their job.
There are no "waiting periods" in federal law. Either your state has added on a waiting period, or the FBI has delayed you for whatever reason. Like I said, getting a "delay" from NICS is completely normal. I know plenty of gun owners who have nothing in their background yet they get delayed by NICS every time they buy a gun. I've also seen people who buy several guns a month with no delay get delayed for no apparent reason.