I have the SAME issue, my holland lop nips at my feet, and gets very territorial when he is out and about in my room. He is about 10 months, and is altered, unfortunately, fixing your bunny isn't always a quick fix (he's been fixed for 3 months now) and they still go through the naughty teen months.
My vet had suggested that I hold his head down (as others have suggested) to show that I am dominant, and to not give the bunny what he wants when he nips (food, hay, moving out of his way) that way he knows nipping does not work. I even put my bunny in his cage for a time out, partly because im so frustrated with the nipping, and to show him that if he does this he will lose out on play time.
as far as yelping, i've done that from day one and it has not worked. My vet told me that in bunny language, yelping means extreme danger or death, so yelping really wont work when it comes to nipping. They apparently, dont respond to noises like that, so perhaps it is a waste of time? please keep us updated, as nipping appears to be a major issue in this forum!