Try an enzymatic stain and odor remover for kid or pet stains. I prefer totally toddler stain and odor remover, or Nature's Miracle. Wet the stinky area and let air-dry. Usually this will get rid of the stain as well but always test a corner first to be sure the fabric can take it. If the smell is still there, reapply the liquid and keep the area wet for a little longer, use a folded towel or some plastic wrap over the spot. If the smell is gone but a stain lingers, try a commercial stain remover for carpet or upholstery, or if the fabric will tolerate it, some dilute laundry detergent on a rag.