Dembele needs to mature. Stop hiding injuries and talk when you feel discomfort. Pretty sure that's how he got the first one.
Don't blame him for the first injury. He was never injured before and probably didn't even knew something could be seriously wrong until it was too late.
If he's hiding discomforts now that's a different story. Our doctors are probably still checking him out after every game though so they would knew if something was wrong. But yeah, it's his career so he should be more responsible now that he knows what he had to go through recovering from a longterm injury. And he's probably also learn a lesson or two about his own body in that time.
Anyway, let's hope it's nothing. He's shown flashes of a brilliant player he could become today.