I took both postinor 2 tablets at the same time though within 12 hours after unprotected sex will it still be effective as my period is late?

It should work, but: Plan B, Postinor 2, and other brands of emergency contraceptive pills can alter the menstrual cycle for the cycle in which Plan B or Postinor 2 was taken, and sometimes the next month's cycle too. One should be sure to check a home pregnancy test about 3 weeks after sex, because emergency contraceptive pills work most of the time, but not all the time.