Your tenant is breaking your lease. The man has no legal right to live there.
You have two options. You may either move immediately for an eviction process due to violation of the lease agreement or increase the rent for as long as the tenant is occupying the unit.
You may give a month-to-month renter a 30- day "no cause" eviction notice, or a "for cause" notice in the case of a lease, which states the violations and the opportunity to correct the problem in the case of a lease.
Or, you may simply demand that the unauthorized roommate go through the normal application process and then you can either approve or disapprove them.