Do i have to wait 5 days or 72 hours with plan b?

Maryevette
Me and my boyfriend had unprotected sex and he dint pull out on time and a few minutes after we were done he gave me a plan b pill do i have to wait 5 days or 72 hours for it to take..... Should i worry about this? Trust me i am really worried about this and stressing out and i havent told him anything yet.