Hi,

I hope you are doing well.

You can appy for IISER in your final year of graduation but you need to meet few  requirements.

The eligibility for  Master's in physics  from IISER should be,

-a minimum of 60% in your graduation

-should have appeared for IIT JAM  and his or her rank should be under 500 .

Below is the link for eligibility bof IISER Pune,

https://www.iiserpune.ac.in/education/admissions/integrated-phd-programme

As you have not mentioned a particular IISER, so I have given you the reference of IISER Pune.

Hope that helps.

Thank you.