If you have sex with someone who finished their chla... - BASHH
Ideally you should wait about a week after treatment before having sex. I would say wait a week or two and then go and get yourself tested as you cannot be sure that they haven’t given you the infection even if you did use a condom.
I personally would go and get check just in case.
Genenrally, if you're being treated for chlamydia, it's important to avoid sex until 7 days after finishing your medicine. This gives the body time to clear up the infection completely to make sure it doesn't get passed on to anyone. Sometimes, the treatment time will be longer after cross infection, maybe need select herbal medicine like diuretic and anti-inflammatory pill or fuyan pill if the inflammation lasts a long time. Get a check just in case.