I sprained my ankle 4 weeks ago. there is still some mild swelling around my ankle & it's painful to extend my foot forwards and backwards. ?

Still healing.: It is important to remember that all sprained ankles are not the same. They are graded in terms of severity. Residual swelling is usually a sign of some remaining instability in of the injured structures. It is sometimes necessary to stabilize the ankle with some sort of ankle stabilization device for a longer time. You might seek the consul of a specialist and raise these concerns.

X-rays or not? : Have you seen a physician and had x-rays yet? The most common causes of persistent swelling after an ankle injury include a small fracture, bone bruising, ligament injury with continued inflammation and/or instability and failure to rehab the injury. If a fracture has been excluded, then avoid overuse, consider use of a brace and rehab the ankle, working on range of motion, strengthening & balance