When Would The Menstruation Start Post Norethisterone?

hi doctor,i had a regular period always but for this month i didn't see my period so i went to doctor and after sonography(scan) he said i have a ovarian cyst in my left ovary and he gave me norethisterone to use 2 of them every night after dinner for 5 days.i wanna know first how many percent may this cyst be danger and also after this 5days i will see my period?