The teenager scored twice as the Red Devils beat Bournemouth 5-2 on Saturday and now has 15 goals for the season.
Solskjaer has vowed to help the striker to continue to improve, saying: “He's a naturally good finisher, so he'll always score goals.
“He's a humble boy, he wants to learn, he listens, he's worked hard, you can see his fitness is getting better and better.
"He's just a young boy who will fill out, he's exciting to work with and we'll keep on building him up in the gym and on the pitch."
On England, the manager added: “If you can handle playing for Man Utd, then you can handle playing for any team and Mason's got the qualities that not many others have.
“So he could play for England's full team or Under-21s, I don't really mind.
“I know he's doing well for us and it's great to have him here."