Does Taking ECP Provide Protection Just After The Periods?

I am a female that just recently turned 15. I have just finished go through my period cycle , & it ended last week sometime. My problem is , last night I had unprotected sex & I'm just scared of the word, "unprotected" . Can anything still happen? . Now my query is , if i take the morning after pill in which i plan on doing will it still take affect on me even though i just recently finished my periods?