Dear Purushotam,

Doctor is one of the repuated proffesion in India.

In order to become a doctor you have to complete your MBBS degree first then you can go for PG degree.

There are three entrance exams NEET, AIIMS and JIPMER to provide admission in medical colleges in India.

You can check the top colleges for medical below

Government

All India Institute of Medical Sciences New Delhi

King George's Medical University, Lucknow

Institute of Medical Sciences Banaras Hindu University, Varanasi 

Jawaharlal Institute of Postgraduate Medical Education and Research Puducherry

University College of Medical Sciences, University of Delhi, Delhi

Maulana Azad Medical College, New Delhi

Private

Christian Medical College, Vellore 

Kasturba Medical College, Manipal

St Johns Medical College, Bangalore

Christian Medical College, Ludhiana

To check the complete list you can refer below link

https://medicine.careers360.com/colleges/ranking

There is a lot of competition envolved to get into medical colleges so make sure you prepare accordingly. 

You can apply for medical exams after completing your 12th class.

Good Luck!!