Given boyfriend yeast infection!!

Patient: Hi, I had unprotected sex with my boyfriend and I didn’t realise I had thrush at the time until the day after. I’m seriously worried I’ve given my boyfriend thrush even though he says he has no symptoms of it. If he has no symptoms, should he not get treated? It’s not an STD because we’ve never been with anybody else. What do I do? Can I buy thrush treatment for him myself just in case or will it damage him if he does not have it? Help!