Dear Ankit, 

In all likelihood, the registration ID and password would have been sent to you on your registered email ID and mobile number. You can retrieve the same from there- the email ID or mobile number that you registered with. 

Furthermore, in case for the option of 'Forget  your password' link, you can undertake two pathways: 

• First, go to http://mbbs.aiimsexams.org/ and then click on 'Proceed to Basic Registration Button'. A new window will appear which is the new AIIMS interface, i.e. PAAR. From there you can login through Applicant login zone. 

OR 

• You can directly go the new AIIMS MBBS interface through link: http://ugcourses.aiimsexams.org/#! and then login from there. There you will find the Forgot your login details option, which can help you retrieve your details. 

Hope that helps. 

All the best!