Open wounds and sores can be caused by a number of injuries and disorders. They can be caused by direct trauma or injury, incisions, blisters, untreated diabetes or prolonged pressure (see decubitus ulcers/bedsores). The term "wound" generally applies to any damaged skin that had not completely healed. Danger lies in wounds that don't heal and are open to infection.
Any wound is at the very least a local contraindication. A simple scrape or scratch needs to be avoided, but the rest of the body can receive massage. Any wound that does not heal or is indicative of a systemic infection would contradict whole body massage.