What can i do to treat minor frostbite on my knee?

Minor?: Not sure what minor means. If you have superficial frostbite, it is treated much the same a a sunburn or abrasion. Monitor for infection, and support the wound so it will heal. If you have blisters or a deeper injury, it would be best to see your doctor. Then, if things don't get better, you will have support at hand rather than having to go to the emergency room. Knee frostbite is not commonest.

Not if minor: Gently re-warming and application of a protective dressing is probably all that is required. There is not much that a physcian can do unless your start to develop problems with vasospastic disease or ongoing pain.