Can you take Plan B while on your period?!?

My boyfriend and I had sex last night and I was on my second day on my period. I’m nervous because the condom broke and he was still inside of me at the time. We pulled out right after since I heard something. He didn’t finish but should I be worried since I don’t know if there was pre cum or not. I know my chances on getting pregnant are very low but should I be very worried and buy Plan B? Could Plan B affect my hormones big time since I’m on my third day on my period right now? Or should I take Plan B when my period is over?!?