I think that your duck has a granuloma.
Some small cuts or wounds heal up unnoticed on their own. Many develop an abscess full of cheesy pus that we call bumblefoot. Some cuts can heal with granulation tissue coming up to fill the space where there was a thorn or pus. That is how the skin...
Fowl is Fair
Put the dogs in the bedroom and bring her in for a cuddle in front of the TV! When I had a needy muscovy, I had to stand by the side gate with him stood on the gate, so he could rest his head across my shoulder.