if a medical student does not get seat in any medical college, what are the other options for him to do next?

There are courses like BDS, Ayush and Veterinary courses which conduct their admissions based on NEET score. These are the only Medical courses available in India apart from MBBS.  Based on the State you belong to, for few courses like BPT, BOT, Nursing courses admissions are through NEET. And apart from Medical courses, being a Biology student, if not NEET, you can always try para medicsl courses, or B.Sc in life sciences. You also can study Pharmacy or Agricultural Sciences. Then there are Psychology, Fisheries courses as well. CBSE has released a list of courses that a student can pursue after studying Biology in 12th and you can check that list at: http://cbse.nic.in/newsite/attach/Compendium%20of%20Courses%20after%20+2.pdf