Hello aspirant

You won't have to write all exams . You will have to reappear for chemistry exam. You must pass this time and make sure you are getting 50% aggtegate marks in three subjects physics,  chemistry and biology.

Then after results you will be eligible for neet.

Neet is National eligibility cum entrance test.

It is held every year as entrance exam for various medical courses such as mbbs, bds, Physiotherapy, nursing courses, bhms, bams and Ayush.

Eligibility criteria for neet

The candidate must have passed minimum 50% marks in class xii with physics,  chemistry and biology subjects as main subjects from government recognized university.

Those candidates will be allowed to appear for Neet who have filled the neet application form.

The candidate must be of 17 years old. There is no upper age limit for neet  application.

For details kindly refer the following link

https://medicine.careers360.com/articles/neet-eligibility-criteria