Nick's biggest problem is that he just refuses to grow up. He is like "Peter Pan!" With everything that has happened to Nick, he just doesn't get the message and it is coming through loud and clear! Nick is a spoiled little boy who wants all of his toys for himself, may be in business, his women and/or even his children. Even when he disgards them, he still doesn't want anyone else playing with them. It doesn't even matter whether he wants them or not. He is possessive and in some cases, obcessive, but with Nick, it is all about him, 24/7 or he wants to take his little marbles and go home. We saw it with how he treated Adam and still treats him and now Dylan, who really has done him nothing.
Nick's problem is that Victor let Nikki coddle him too much. Now, he expects every woman in his life to treat him like his mother did and that just isn't gonna happen.
What he is doing to Dylan is stupid and uncalled for. But then, I am beginning to think that Nick is stupid and uncalled for.