False FIR against my wife

My wife is working and lived with my younger son (3.5 years) at a second residence of us. Myself and my older son (7 years) used to stay with my mother during weekdays (because of the distance between our workplaces)and during weekends we used to meet. One day she protested against loudspeaker playing in a nearby house and told them to stop since my younger son suffered from pneumonia he could not sleep. After repeated requests she called up the police and after calling repeatedly to the police station, police (SI) arrived and threatened my wife by saying "I will lodge complaint against you and will stop your salary"(it seemed that he was furious as my wife tried to contact local police station repeatedly . My wife staying alone at that time was nervous and after two days we came to know that an FIR was lodged against her. The FIR was false and accused her that she (allegedly) shouted at the loudspeaker players and thrown stones etc. etc. Later on I came back home and contacted senior police officers, who were helpful. and they came to my house and talked to us and said that she can not be guilty after investigating the place and assured us to give an FR and no chargesheet will be given against her. Now what can I do against the false complainer? or the involved SI? It is a mental agony until we get the FR. The opposite party gave a notary affidavit to the police station (that they have no complains), will that be enough for police to give a final report/cancellation report. We left the place for security reasons and now we are staying together. We dont have a copy of the notary affidavit given by the opposition to the police. Should we trust the senior police officers? Should we go for a defamation against the opposite party (now or after getting the final cancellation report) for a false FIR?