Don't worry, it's a small gain and it might be just what you need to give you a kick up the backside to get serious about your weight loss!
It's okay to have small indulgences now and then, but sounds like it was just a bit much.. maybe limit your indulgences to special occasions, so you can plan and look forward to it? Like.. I'm going to a wedding on Sunday, so I'm really looking forward to having a couple of drinks and eating the delicious food at the reception - and that's helping keep me on track for the rest of the week
Remember, it's what you do MOST of the time that determines the outcome. If you're eating healthy and exercising 80-90% of the time, that will show up