You are still going thru the honeymoon/new phase with your bird. Alot of it will be patience. I would not allow your bird on your shoulder because it makes the bird think he/she is top bird in the flock. Until he/she is trained which wont be for awhile I would never allow them on your shoulder. So basically the nipping probably is associated with your bird trying to be dominant over you so just block them from going on your shoulder. Although expect to be bitten a few times during training it hurts but dont show fear. Lots of people do a technique called 'the earthquake' when their fid is on their arm and trying to move up to the shoulder or doing something they shouldnt be doing while on the arm....its shaking the arm up and down to grab their attention. Sometimes if you push forward into the bite that also stops them. My fid has not bit me for ages due to the fact he thinks it doesnt hurt me lol.
The other thing you might want to think about is that you might be over stimulating your new fid. He/she needs time to adjust to the new place, new sights, new sounds etc and alot of it can be over bearing for them at first. This by all means does not mean that you should just stop paying attention to the bird but perhaps only give it the amount of attention you will be giving it on a regular basis after the novelty of a new bird wears off. Mostly just talk to the bird alot near the cage so it gets used to your voice and when you do take him out to train take him to another room away from the cage so he isnt always trying to get back there. Look for signs the bird has had enough during any training session and take him back immediatly. That way your bird will be more eager to come out the next time instead of thinking gee humans are a drag and boring.
good luck with your little fid