Just like everyone else has said, ONE bad day does not ruin a diet. What is important that you start fresh at the next available opportunity (the next meal, the next day, the next minute)!
Remember, you didn't get overweight by eating bad for one day, and one bad day is going going to make you gain back everything you have lost. Even if the scales go up, it is more likely a gain from fluid retention (Chinese food seems to have a lot of salt in it) or simply the weight of the food you ate. It will come back off as it is digested.
YOU CAN DO IT!!!!!