Sorry that I was kinda short with my reply earlier. For my opinion, go ahead and brew tomorrow and pitch that smack pack. Early on, I brewed several beers without appropriate yeast count... Several which have been great beers, so brew confidently.
"Yeast starter" might be a misleading name for a newer brewer. "Yeast readier" might be a better name. The goal of the starter is to achieve the appropriate yeast count for your original gravity. From what I understand, Wyeast smack packs and white labs vials are ready as is for a beer of a gravity of 1.040. I like to give my starters enough time to finish out so that I can cold crash them in the fridge for about 24 hours and decant the spent beer off the top of the slurry
You didn't make a mistake, you had a great learning experience. A mistake would be like when I forgot to add my whirlfloc tab to my last IPA that I used a pound of hops in. I'm sure others will weigh in and give their excellent advice too... Welcome to the forum! I've learned much of what I know about brewing here!