Welcome to the forum, Dino and Cadbury (great name!). Wolf is correct. In my personal experience, GCCs are either the sweetest, most affectionate and docile little birds or bitey little devils
But, in their defense, all the birds that bite do it because their needs are not been satisfied. You see, GCCs are not easy birds to keep because, like cockatoos, they require an inordinate amount of time spent on them as well as a low protein, low fat, high fiber, high moisture diet and a rigorous solar schedule.
Without the answers to the questions Wolf asked and which would give us a more accurate picture of what is going on, I can't tell you for sure what is happening but, if I were to speculate, I would say that he is frustrated with you BIG TIME! It seems to me (again, I am speculating) that you don't spend enough time with him (they need about 4 hours a day of one-on-one) and, because he is, most likely, kept at a human light schedule and is been fed too much protein (pellets are not good for them), he is now sexually frustrated and, because his human (you) is not giving him what he needs (he can't even get to you when he wants), he bites you. It happens all the time with them. I've had four of them, have one right now and will, most likely, get another one soon and all of them (including the one that might be coming) were given up because of aggression (one of them also because he screamed all the time) but, once they started getting their needs satisfied all the time, they never it again. My Codee is the sweetest, sweetest thing! She is, pretty much, the only bird that I allow my grandkids to handle because she never bites or even nips. And the other ones I took in and which I rehomed after rehabilitating, are still today doing great in their new homes.