Dhruv should not have done this. But he did it in the heat of the moment. He was fustrated, scared seeing Nandini in danger, anger and he lose control over his temper and punched Manik. Dhruv is gonna regret it. And Manik will be hurt. But I believe their friendship is strong enough to survive. It happens in real life too. Sometimes we say many bad things in anger but people who truly love us get hurt but understand it. And the person who says it feel horribly guilty after he calm down. That's gonna happen here too.
But yes thnks to Alya a crack has been made. Maybe the four will survive the storm and stay together. But Alya won't be able to survive it. And Harshad is gonna make full use of this crack. And that stupid Navya is gonna help him. She is very selfish.