When my feet get really cold, lumps form on the bottom, kind of like there is swollen spots. What is this and how can it be treated?

Hives. Can form on any part of the body that gets too cold on some people. This is called cold urticaria. This is considered like an allergic reaction and could be controlled by preventing getting the feet too cold and taking antihistamines. You should get an evaluation to look for any other medical reasons such as circulation or nerve damage.