Tony is aware of Nicole thru Kristen portraying her. However, Nicole has been around for a lot of years, and they may not have interacted storywise, but knew each other. Days had a bad habit of having Andre impersonate Tony so it is hard to remember exactly. Heck all those years "Tony" was in Salem, only then the writers decide to have had him on some island for all those years, Andre pretending to be him. And John & Marlena rescued him, if I remember right, Anna was along because she would know once she kissed him, if he was really Tony.