OMG! Don't worry! A tbsp butter and a baked potato won't kill you. In fact, recent research shows that white potatoes have very good nutritional value, It's true, sweet potatoes have more n.v. and lowfat sour cream has less sat fat than butter, but if you enjoy it once in a while, it's fine.
But as it stands, it's not a well balanced meal. Consider topping with a protein (melted cheese, veggie crumbles-easy to microwave a small serving, etc) and salsa or broccoli or serve with a a side salad for a bigger nutrititional bang.