Swelling in the leg after a warm water bath is only incidental. Even if swelling occurs because of warm water, it will be mild. I only hope there is no infection at the site of injury
which can result in considerable swelling. You must consult the doctor who stitched you up at the earliest and get the wound examined. There may be some collection as well which should be attended to as soon as possible. Do not keep the leg hanging down as that may also cause swelling. Rest it horizontally on a stool while sitting.