I'm so sorry to hear your boy has decided to let his inner diva come out! :lol:
Most behavorists will tell you that a dog that acts like yours is in social situations is doing it out of fear. Since he's just a pup still, he may be going through his teenage angst years as well, testing to see how far he can go.
Vic was right about the dominance; if he's confused about the dominance hierarchy, the barking might be caused by him not knowing who's in charge. Try this simple dominance-gainer and see if it helps:
When you feed him, make him sit (first, teach him to sit. LOL) before you put down his food. Put it down and if he gets up, take the food away. It'll take a while for him to figure it out but the gist is that he sits until you tell him he can eat. Once he does sit and wait, the next day, make him sit a bit longer. Just 10-20 seconds is all he needs to wait - long enough for him to realize YOU are the one that controls the food, therefore, you are the one in control.
If you have other people in the house with you, have them do the same thing so he views all of you as his pack leaders. If it doesn't stop the biting and nipping, then at least you'll have dominance figured out in the end.
Puppy classes are a must, in my opinion. They're more for the human than they are for the dog. Cooper is the first dog I've owned all my myself so I thought
I knew how to do certain things... I found out my ways were all wrong. They really do help form a bond between dog and human, as well as giving you good tips on how to handle just about anything. Your pup gets an opportunity to get some socialization with unfamiliar dogs in as well.