Remember what I went through with MONTY lovesduckies ??? That was all hormonally orientated, and also partially because he was a hand raised duckling. But with training I have been able to stop him attacking my feet everytime I walk outside the back door. You have to ensure he knows you are the dominant one. You dont have to be cruel to be kind- If he starts biting or nipping again try and hold him. Keep his wings down so he cant flap and hurt you.. But if you can hold him and hold his beak- then turn him over onto his back for 1 minute or until he can roll himself back over- which ever comes first. It will not hurt him to by put on his back for 1 minute. But it will train him to know that if he bites you he will be turned onto his back. It worked with Monty in just a few days. Dont leave him alone or for longer than a minute, and see how it goes. It worked for me. If you dont feel confident with this, maybe you could have an area to enclose him. Lock him away in a small area away from you and quackers for 5 minutes each time he bites you. Put him in the bath tub ( no water ) or a similar place.
Just remember normal duck rules dont apply when you raise them in your bedroom - he will display behaviour better suited to outdoors- dont lock him away for that... Only when he bites or attacks you. Leave him be with Quackers...they are only doing what comes naturally.