THC is usually only tracable in saliva for around 8 hours. Make sure you brush your teeth really good, use mouthwash, then peroxide.
As far as the violation, be honest with your PO, and hope for the best. It most likely is a violation, but it doesn't seem like the cop gave you too much trouble so you should be good.
Did someone say lie to the PO and say he got a parking violation? Really? Like the PO doesn't already know he doesn't have a license.....