I provided photos to a waterfowl rescue and rehabilitation center. They also suggested it was a bruise and should go away on its own. I have been keeping careful eye on my Lucy. She is still active, eating and drinking. She does not show signs of discomfort or pain. So I will just wait and see...
one of my 6 weeks old babies woke with the same thing. No other problems though. She is eating, drinking, playing, swimming all as normal..I have tried to research this and found NOTHING. It looks as though its bruised, and is soft. =(