Tutoring, student does not pay
This is a private business transaction between you and the student.  Neither the university nor the professor was a party to that transaction, so they'll have no interest in interfering, and it would be inappropriate to try to involve them.

Anyone who provides services to clients for money will eventually find that some of them don't pay.  You can see many examples, and suggestions for ways to collect, on Freelancing.SE.  To say more here would be off-topic, I think.  I'd just keep in mind that pursuing your non-paying client will require more of your valuable time - make sure it doesn't become disproportionate to the amount of money at stake.  At some point, the most cost-effective approach may be to just let it go.