Unless you're experiencing cravings, just get back on the wagon
Slip ups happen from time to time, just as long as you don't let that one little slip up snowball until you're all the way at the bottom of the hill...you know, the pieces of fudge turn into a pack of cookies, a pack of cookies turn into a whole sheet cake...and so on...you'll be okay.
If you're experiencing cravings, I'd go back to Phase I for a few days (at least 3) until the cravings are gone.
Hang in there and good luck