NEED SOME ADVICE ON PLAN B

so my boyfriend and i were having sex but all of a sudden he stopped because he heard a pop, well turns out the condom tore on us (mind you that he hadn’t came yet but it was our second time this night and he wiped himself dry but i know there might still be a chance because of pre cum) we rushed to buy a plan b pill and i took it as soon as i opened it. what side effects should i watch out for, any advice on this situation? (i’m aware that it’s not 100% effective and everyone’s body is different but i’m very worried)