Nancy is in the North-East of France, and not far away from Belgium, Luxembourg and Germany. You can go to these location by train or by car sharing.
Brussels (left) and Luxembourg (right)
You might also want to visit some other French cities. From Nancy, you have multiple possibilities. You can go to visit Paris by taking the TGV again, or you might want to see Metz, a city the size of Nancy and 40min away, or Strasbourg, a more german city in Alsace, France.
Metz (left) and Strasbourg (right)