I want to take CSE B.Tech in a well-known college, but my JEE Mains score is poor. What should I do now?

You can Take alternative engineering entrance exams, like BITSAT, VITEEE, SRMJEEE, and AEEE, hold their own entrance exams for admission to B.Tech programs. Their is another option for you is the, you can take drop and study better and Gain good marks in next year. You have two option, choose wisely