To do or not to do? Iui this time?

We were planning to do iui#2 this cycle 05/31, but Saturday I forgot to take my Letrozole on time:(. Took 2 with 12 hours apart Sunday. The pharmacist said it was a way to take a missed doze. The nurse Monday morning said: she's recommend just going days 4-8, instead of 3-7... Now I'm scared: would this ruin our chances if we try iui? This will be our 2nd try. And I messed up the first time around same way.