Will Taking Plan B After Having Unprotected Sex While On Periods Be A Problem?

Hi, I was wondering if it would be necessary to take Plan B if I just started my period yesterday, and my boyfriend and I were having sex today and the condom broke and he ended up finishing inside of me. Will Plan B mess up my period? And would it be the necessary precaution? Or am I safe to wait and start taking my birth control again when my period stops, like I regularly do? I am regularly on birth control and let my body menstruate each month, and that is when this happened.