"It's a reward after a difficult spring," the Sardinian star said after claiming his maiden Tour de France win.
Three-time Tour winner Chris Froome took the leader's yellow jersey from teammate Geraint Thomas after finishing third.
Froome now leads Thomas by 12 seconds in the overall classification, with Aru trailing just two seconds behind.
"Beating Froome will be hard but I'll try," the former Giro and Vuelta champion said.
Meanwhile, another of the pre-race favourites, Nairo Quintana, ran into trouble and is now almost a minute behind Froome.
With ANSA
