Will I gain weight from eating 2000 calories today?

According to my nutritionist/dietician I'm supposed to eat 1500 calories a day and exercise 3-5 times a week. Today I exercised, burning about 500 calories... but I ate 2000 calories. Will I gain weight? Even if it's like 1/4 a pound I still need to knowwwww. Help. And some of it was peanut er, like 3 tbsp. so that's a lot of fat... do you think that will make me gain weight?