It depends on what kind of injury the other party has suffered. Generally speaking, a stab wound will constitute a minor injury.
What if it constitutes a minor injury?
If you call the police: the public security bureau accepts the case, the consequence is that your brother has a criminal record, that is, he will be detained. And then wait for further processing. Civil compensation is still necessary.
If you don't call the police: if the negotiation fails, the other party is likely to call the police, which is also the consequence of the above. If the police don't accept it, the other party will sue to the court. If you still don't actively compensate, your brother will still be punished accordingly.
In short, at present, this matter can be big or small.
Legal way: Your brother has a criminal record, and the compensation may not be as much as the other party wants.
Settle: only meet each other's requirements.
You can weigh the pros and cons yourself.