Getting swelling in one leg and ankle, with no injury, no pain?

Injury. One-sided swelling in leg and ankle is usually associated with injury, but a condition called chronic venous insufficiency may also be the cause of it. Try elevating your legs and if the swelling goes down, its more venous than injury. See a podiatrist for a more thorough evaluation.
See a doctor. Swelling in one leg is an unusual circumstance with out some type of injury. You should see a doctor to have it checked.
Visit a doctor . There are many possible causes for this, but swelling of a leg without an obvious cause should be evaluated by a physician. One cause we always worry about is a blood clot. A delay in diagnosis of a clot can be quite risky.