Help!!

Destiny
So tonight I had unprotected sex and the guy came inside of me. Usually, if I'm far enough away from my fertile window I don't worry, but I checked <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> on the way home and my fertility window starts tomorrow. Should I take a Plan B pill or do y'all think I could be in the clear?!