Cut the melted-looking spot on the sofa from the leather with a utility knife. Carefully run the blade across the couch, outlining the melted area. Go over the marks several times with the knife until you have cut out the damaged leather.
Lay a piece of leather in a matching shade over the top of the cutout. Trim it with the utility knife until it covers the spot with the missing leather, overhanging it by ½ inch or less.
Apply a thin layer of fabric glue to the edges of original leather surrounding the cutout. Gently place the new leather on top of the glue and press down. Smooth it with your hands, pushing out any air bubbles and making sure it sits evenly on the couch.
Wipe the edges of the new leather with a damp cloth, removing any fabric glue that seeps through the edges. Rub the cloth over the edges and let the repaired area dry overnight. The small amount of water should not damage the leather finish.
Remove the color sealer from the leather repair kit and shake the bottle gently in your hands. Apply a thin coat to the edges, where the new leather meets the couch; let the sealer dry. It will cover the seams and help hide the repair.