For what it's worth, I did almost the exact same thing last night. I ate a small noodle when cooking pasta for my kids. My husband and I were eating the same meal but used zucchini noodles for ours. I didn't even think about it until I was sitting at the table and it just hit me! I ate a noodle to make sure it was done! Darnit!!
I've read the "should I start over" and made the decision for myself not to. I WILL be more cautious when cooking (my husband does most of the cooking, so it's not a habit for me yet) and I don't think my journey with whole30 will end at 30 days anyway. So I will continue to take what I've learned and may go past 30 days as it is. But I don't feel like I "Failed" or made a bad choice and for my own sanity, decided I don't need to hit the start over button.
Now, if I was sneaking a bite of my kid's food because I really wanted it (which I seriously was tempted to do while making them mac & cheese for lunch), then I would treat that differently. I wasn't giving into anything and slipping up and falling into a noodle. It was just habit and not intentional.