Missed one birth control pill? Possible pregnancy?

I was supposed to start my new pack of birth control pills yesterday ( sunday ) and I ran out and didn't realize until late last night. They won't have my new prescription ready until tonight ( Monday ). What do I do? Is there a chance I will become pregnant?

Most unlikely, however, if the possibility troubles you, you can abstain from the 9th through the 21st day after your last period started for extra peace fo mind.