You can use Cottage Cheese as a substitute if you run out of Sour Cream, here's what you need to do:
Put 1 Cup Cottage Cheese in your blender
Add 5 Tablespoons Milk (whatever you have)
1 Tablespoon Lemon Juice
Blend until creamy and you've got substitute sour cream!
Check out my recipe to make your own Dried Onion Soup Mix, mix with your substitute Sour Cream and you've got a quick, yummy dip!