I still couldn't get stamp on my passport for my application. Is that a problem if I have to show my passport to police? Because my visa is already expired.

If the application was sent by traditional mail, in order to meet formal requirements and receive a stamp, you must wait for an appointment at this office to complete any missing formalities. In case of a police check between the expiration of your visa and the receipt of the stamp in your passport, you may provide, for example, the case number, the date the application was sent to this office, and the type of application submitted. The Police and Border Guard will be able to verify the information provided.