I put my nuvaring in a day late and had unprotected sex after it was only in for a day. Is my chance of pregnancy high enough for me to purchase plan B?

Any time you have sex, whether you are protected or not, there is a chance for pregnancy. How long ago was this? Plan B is meant to be taken as soon as you notice a problem with your contraception. It's effectiveness decreases the longer you wait to take it. Plan B can not terminate an existing pregnancy, it can only prevent one. So if you already conceived it will not work.

This was yesterday