What happens when I miss a pill??

I went to take tonight's pill and I noticed I was taking Sunday's pill (today is a Monday), which means that I missed a pill sometime this week. I have no idea which day it was, meaning I couldn't have doubled up, and I'm pretty sure that's what you're supposed to be doing when you miss one.

Do I just pretend it never happened? Are there going to be changes to my cycle? I've never missed a pill before 😬