Will I be protected?

So I just refilled my pill rx after not taking BC for almost a year. I forgot that you're supposed to start it on the first day of your period, but can I not just start the pack a few days in? Like is it necessary to start taking them exactly on the first day to be effective or does a certain amount of time just have to pass with you having taken it consecutively (like a week or a whole month) to be effective? I just want to have it be effective ASAP and don't want to wait another 3 weeks for my next period to start taking it.