.

[Curious Diode]

This post has been overwritten by an open source script.

[liz]

Four days is a very very short time. He is still afraid of you and his new strange home. You have not learned his body language is why you are getting bit. I don't know Conure hormonals and how early it happens so I can't help you there. Some one else will post with more info.
A 2 year old has already developed his own personality. Do you know any backround? If he climbs to your shoulder he depends on you even if he does not trust you.
Don't ask anything of him. Try not to touch him. He will come to you when he is ready. Let him claim you as his human instead of you claiming him as your bird.

Others will post and give you more info than I can.

[Curious Diode]

This post has been overwritten by an open source script.

[Wolf]

Without having more information than we have it is very difficult to say what is happening and we have to sort of guess based on what you have said, which at this point is not much, but never fear we don't mind asking questions if it will help your bird. You seem to know that your bird does need some time to adjust to its new home but not enough about this process so it is as good of a place to begin as any.
When you bring a bird home with you, the bird is terrified as everything that it has ever known has changed and he is all alone in a new environment with strange new giant people that he doesn't know or trust, yet he knows that he is dependent on these strangers for everything. This is a difficult thing for a parrot as he is dependent on his flock for his safety and sense of security. In his natural environment this is almost certain death for the bird and although he is captive bred and raised, he is very much aware of this.
Unlike a dog or cat, who will almost blindly trust anyone who will feed and pet it a parrot does not trust so easily and you have to earn their trust over a period of time. Depending on how you interact with your new bird, what its past was like, the birds personality and other factors this process could take a month or more before the bird actually begins to trust you. If the bird is allowed to come out of its cage daily to look around and explore its new home then it will probably take it about a month to begin to feel comfortable in the new environment, it could take longer and although not as likely it could take less time.
It is possible that this aggressiveness is due to his being hormonal, it is possible that it is because he wants more time with you. It is possible that he does not like you to reach into his cage and is trying to tell you to open the door and allow him to come out on his own. There are many possibilities for what is causing this behavior. I am not going to be able to finish this post as my birds are beginning to move about and ask for their breakfast, so I am going to post what I have here and come back to continue after I address my birds needs.

[Pajarita]

My dear, four days is NOTHING! The poor bird doesn't know you from Adam, much less trust you and that's why he is biting you! He could be hormonal, too. He is at an age when they go through puberty and, if he was kept at a human schedule and free-fed protein food (seeds, pellets, nutriberries, avi-cakes, etc) he most likely is quite uncomfortable which does make them bitey but the biggest problem here is that he hasn't bonded with you. So, if I were you, I would stop physical interaction with him until he learns to trust you (love will come later) because, right now and although he does like (and need) to be touched, you are a stranger to him and nobody likes a stranger taking liberties, right?

I would also stop all training. You need to bond with this bird and training does not do it. Once he trusts and loves you, you can start training him but not before. It is completely counterproductive, in my personal opinion. Parrots are not mentally hard-wired for obedience or have a need to please as dogs do so training requires bribing and their compliance (and this is only given gracefully when they love us). Open his cage so he can come out. Place perches on the outside of the cage or a playtop on it. Talk to him, sing, whistle, offer treats, etc and, if he wants to come on you (don't ask him, wait and see if he does -they bob up and down when they do), allow it. He needs, at the very least, 3 to 4 hours daily of one-on-one time. GCCS have an undeserved reputation of been bitey but it's only when they don't get enough attention (they are as needy as a cockatoo!) that they do bite or scream.

[Curious Diode]

This post has been overwritten by an open source script.

[Wolf]

Looks like I am a bit late in getting back to this and it looks like Pajarita took it to where I was headed in my post and a bit quicker than I was doing it. Ah well it doesn't matter as long as you got the right information.