You can initiate legal proceeding against him for the offence of rape and cheating. He has committed the rape by the misconception of fact. At the time of giving that promise, he had no intention to marry thereby he has also committed the offence of cheating. Lodge an FIR against him under section 376 and 417 of the Indian Penal Code.
Lodge the first information report
The statement of the rape victim is sufficient to lodge the FIR against the accused. You should know the procedure towards the recording of FIR. No need to reduce any direct evidence at the time of lodging the FIR. Despite that, you should prefer some circumstantial evidence to prove that the accused had the opportunity to commit rape. Section 154 of the code of criminal procedure provides that FIR about rape should be recorded by the women police officer. Therefore, you can file the FIR in the Mahila Thana of your district.
Place of occurrence and territorial jurisdiction
You should file the FIR in the police station which has the territorial jurisdiction over the place of occurrence. The place of occurrence is the place at which your boyfriend has committed rape. If you give the information in the police station who does not have territorial jurisdiction then it will not initiate an investigation. In this condition, the police officer will record the zero FIR.
Rape and cheating
He has committed the offence of rape and cheating because he took your consent by the false promise of marriage. Consent is a very important fact for the offence of rape. If you have given the consent with your free consent then you cannot initiate any legal proceeding against him. When you knew the facts that he will not marry you then again your boyfriend is not responsible. Section 376 of the Indian Penal Code makes the rape an offence and it has some legal technicalities.
Rape is a cognisable and a non-bailable offence. When you lodge the FIR and police officer has reason to believe that offence has been committed then he will start the investigation immediately. Since the offence is cognisable hence, the investigating officer will arrest the accused.