if the landlord entered your apartment secretly for a purpose other than for making repairs or another emergency, in my opinion that would be grounds for termination of your tenancy. You have a few options available to you. On the criminal side, you can file an application for the issuance of a criminal complaint. This will require you to go to the district court for the area where you live and "swear out" a complaint. On the civil side, you can sue the landlord for something called "breach of quiet enjoyment", for which you would be entitled to damages in the amount of 3 months rent as well as attorney's fees. Finally, in my view you would also be eligible for damages for the cost of your move, any emotional distress you suffered from feeling "violated" by the landlord's unlawful entry into your apartment, and any increase in rent you would have to pay for any apartment you move to. Please feel free to contact me if you wish to discuss this further.
If you want criminal action to be taken you should call the police. They can file criminal charges against your landlord. If the police takes no action you can go to the clerk's office and file a criminal complaint and do it by means of a clerk's hearing.
Attorney Jason Chan