Dear Varsha, you can pursue Masters in Physiotherapy in various mainstreams like Neurology, Cardiology, Orthopedics and Sport Sciences. There are universities in India which offer a mix of these mainstream fields. Please go through the Affliated University website for specicalizations in MPT of your particular state. Or, if you want us to jolt them down for you, please mention your state and we will help you with that. 

However if you want to give it a try at AIIMS entrance exam, according to their website at http://mbbs.aiimsexams.org/Home/Eligibility, you should have been 17 years old as on December 31st, 2018. AIIMS has completed its counselling and filling of the seats for this accademic year. You may have to give it a shot in the next accademic year.. 

And coming to the part which is good for you, I think you should certainly follow your passion. Hardwork when combined with passion, gives you results. Give it your best shot so that when you look back, you should have no regrets. You should be satisfied with the results no matter what they are cos you know that you gave it all.. Good luck!