As per the guidelines issued by National Board of Education(NBE), it is no longer mandatory to have temporary registration with MCI(Medical Council of India) at the time of writing NEET-PG. Foreign nationals are eligible to write NEET-PG without MCI certification. The MCI, on payment of the prescribed fee for registration can grant temporary registration for the duration of the Post Graduate course. It's limited to the institution to which the candidate is admitted for the time being exclusively for pursuing postgraduate studies.

The Temporary Registration(TR) to such foreign national shall be subject to the condition that such person is duly registered with appropriate registering authority in his own country where from he has obtained his Basic Medical qualification. And such institute should be duly recognized by the corresponding Medical Council or concerned authority. The candidate should've completed the requisite internship on or before 31st March of the year of examination.

In case you're an Indian student living overseas then,

An OCI(Overseas Citizen of India) is eligible for NEET-PG who have completed primary medical education(from anywhere outside India) and must have given the Foreign Medical Graduate Examination(FMGE) conducted by the National board of examination(NBE).

The candidate must have completed the requisite internship on or before 31st March and must be registered under the Medical Council of India(MCI)/State Medical Council(SME).

For more details please, follow this link: https://medicine.careers360.com/articles/neet-pg-eligibility-criteria