Can swaddling a new born cause bruise like marks on the tummy area?

Possibly : Swaddling even when tight generally does not cause bruising. It may be the diapers (too tight or allergic reaction), clothing, or a normal newborn rash called erythema toxicum. These should spontaneously resolve. If you notice more bruising or if they don't resolve as expected go see your pediatrician.

I've never seen it: The more common reason for a bruise looking area would be a stain from triple dye used on the umbilical cord if used in your hospital. Another source might be a deep blood vessel birth mark under the skin. Mongolian patches can look like bruises but they are found on the back, not in front.The only other source i can think of would be trauma & real bruising.