As of now , since i-pill  was taken within 24 hrs, there is no chance of pregnancy and you might get withdrawal bleeding before your expected period.But if unprotected sex occurs after 72hrs of i-pill and during unsafe period of your cycle,( which varies according to , once in how many days you get your period, if it occurs  once in 28 days, unsafe period is between day10 to day 20), then  please Note ,then chance of pregnancy is there.