condom broke


my boyfriend and I had sex tonight and the condom broke and we didn’t realize for a while. it was still towards the beginning of sex so he hadn’t cum yet but i’m worried about pre come. I had my period about 2 weeks ago and according to this app I am in my fertile window but on the tail end of it. what are the chances of me getting pregnant? should I take a plan b pill just to be safe? please reply and let me know asap. thanks