My dr tapped the ankle and he heard a rattle after i had a bad sprain, what does that mean? 3 weeks later it is still very sore.

Rest and elevate: I really don't know what the rattle is, but I am sure that the doctor immobilized it in a brace or a fracture boot after he taped it.. If not, it probably needs to be done. Also, you need to rest it and not exercise it while it is still hurting. The soreness is your body's way of telling you that there is something still wrong.

Physical therapy.: You may require physical therapy, to strengthen the ankle. ask your doctor if that's an option for you.