Its an important peice of evidence. However it depends upon the doctor concerned to refer the case to police for its registration as an MLC case. Basically it depends upon the patient as well as the doctor. Doctor is duty bound to register the case where particular category of offence is made out. He may not follow the protocol by not registering mlc when same is requested by the patient itself. reason/request is supposed to be maintained by him in order to defend his case for non reporting to police authorites.
You may ask for the particulars of the case under RTI as to whether case has been registed as MLC or non MLC and if no, what was the reason noted by Doctor not to report such case.
Regarding the use of such evidence, i think it may be used in important reference to the offence and it may co relate the incident.
Consult your lawyer regarding further course of action