Will plan b irregulate my cycle and bc?

Okay so I’m starting birth control after my next period. So my bf and I had sex and the condom broke (he didn’t cum just precum). Now getting pregnant from precum is rare but it happens so he freaked out which freaked me out. So he suggested plan b just to be safe. So I asked my mom and my aunt and they said I’d be just fine and plus plan b would mess up my cycle and my hormone levels would be messed up for my birth control. But I just had this gut feeling that I shld take it so I did. My mom actually got pregnant with me from precum so I wasn’t taking any chances. So will the plan b mess up my cycle and can I still start my birth control?