The teen struck in victory over Atalanta this week.
"We have had requests from a lot of teams, but he is staying here," Galliani told Milan Channel.
"I talked to him and his agent and told him to remain calm. And he will find his space.
"Indeed, we are not so short in midfield with him and the fact is that we have Muntari and Montolivo suspended in the Champions League, and in the first leg [Last 16] against Atletico Madrid, Cristante will play."