Need ultrasound. Lack of symmetry in leg swelling should first be evaluated by an ultrasound to assess the source of the problem. A clot found in a deep vein (DVT) would require blood thinners for at least 3 months since these clots can sometimes break off and travel to the lung. If no obvious abnormality can be found the problem can be addressed through leg elevation, compression stockings and maybe diuretics.
One leg swelling. Unilateral leg swelling requires an evaluation with including physical exam, venous ultrasound and, possibly, CT OR MR. Bilateral leg swelling is often times due to an underlying medical problems such as heart, kidneys, liver or lung. Unilateral swelling is usually related to something on the side of the swelling. See a vein specialist to begin an evaluation and start to wear compression hose.