I got level two frostbite on both of my hands and they constantly swell up. whats the reason for this?

Lymphatics: Your lymphatic vessels have likely been traumatized. I would recommend a compression garment for your hand and arm. Prior to that you should seek the opinion of a vascular specialist about lymphedema treatment.

Vessel overactivity.: Frostbite alters response of the small arteries to cold: they tend to become hyper-reactive and constrict with repeat exposure to cold. This gets better overtime, but very slowly. Best strategy - avoid exposure to cold - use warm gloves or mittens.

Lymphedema: You may have had sufficient injury to the lymphatics that they are not functioning well. You probably would benefit from compression therapy and then compression garments to control the swelling.