Generally, it is always advisable to exhaust all available remedies, that is, try to settle amicably before approaching the courts. However, self-help that involves acts of violence is not an option and should be avoided.
In the event of breach of the right to freedom of assembly, an official report in the form of a notice of breach of right and the damage done, if any, should be made to the appropriate authority.
In the case of harm or disturbance by a police officer, report should first be made to the Commissioner of Police.
TIP: to do this:
Contact a lawyer, human right organization or NHRC for assistance.
Notify the appropriate authority in charge of the offender, attaching the medical reports and pictures to the notice. You could ask a lawyer to write a petition to the authorities in charge of the offender (the AIG or Human Rights Department of the Nigerian police Force, in the case of an offending police officer).