A boy of privilege from elite schools, Cary probably never perceived his behavior as immature. After all, the wealthy are shielded from having to look too hard at themselves to survive. When he interviews to return to the law firm which rejected him two years ago he admits that he has grown up. That means he knows he acted like a jerk there. Although Will pushes to block his return, return he does.
At the bar, Cary and his former enemy Alicia act cordial to one another. Also he and Will call a truce. However, we know human nature. We can expect tension at the very least and backstabbing at the worst.
This was the April 22nd episode. I had just gotten to my Tivo.