This speech has been given hundreds of times on this board, so first know that you're not alone. This happens to ALL of us. All of us. Those of us who weigh daily just see it more often, and we're the ones who have to get used to the fluctuations on the scale.
You say you didn't eat a super healthy dinner. Depending on what it was, it could be that even though you stayed in your calorie range, your sodium is up from less-than-healthy food and you're retaining water. If I eat pizza, for instance, even a reasonable portion, I am always up a couple pounds the next day.
Salt and carbs both can make a lot of us retain water. Just drink your water today and you'll probably see a loss again tomorrow. The good news is you haven't gained back two pounds of fat! You're doing great, and you'll see the number go back down over the next week as well. (And once you figure out your body's weight loss pattern, you can choose your natural 'low' day as your 'official' weigh-in. Mine happens to be Wednesday.)
In the meantime, read this post on weight fluctuations: Weight Loss Fluctuations
. It will explain a lot and hopefully help you feel a little better.