You only need to restart induction if you find that eating the banana bread is triggering cravings for more carbs. Otherwise, just get back on track and keep doing what you were doing. I had a little slip-up with banana bread myself a while ago (at a friend's house). It didn't trigger cravings and I just went right back to ongoing weight loss the next day.

Congratulations on your success so far! We all fall off plan occasionally. The important thing is to pick yourself up and get back on. It's when one slip up leads to another that people get in trouble.