How To Contact The Nigerian Police
If you have been scammed by a Nigerian and have reasonable proof of this (not a suspicion). You can contact the Nigerian National Police and file a report. The Nigerians do investigate cases of Internet Money Crimes, such as 419 money fraud and Dating Scams.
However, you should note, that in all probability, nothing will happen. You should also use the other tools here to report the crime to the FBI and IC3. Not only will you have done the right thing, and by keeping copies of your reports, you also will have the ability to claim a tax deduction for your loss.
The following provides the Nigerian Police contact information, and help in reporting crimes.