If you forget the nuva ring for first day of the week?

If NuvaRing® has been left in your vagina for up to one extra week (four weeks in total or less), remove it and insert a new contraceptive ring after a one-week ring-free break. If NuvaRing® has been left in place for more than four weeks, you may not be adequately protected against pregnancy and you must check to be sure you are not pregnant. If you know or suspect that you're pregnant, do not use NuvaRing®. If you are not pregnant, insert a new contraceptive ring. You must use an extra method of Birth Control, such as male condoms or spermicide, until the new NuvaRing® has been in place for seven days in a row.

This is from the Nuva Ring's website.