Hi Jatin!
JEE means score is valid all over India and is extended to all the colleges in the India which offer B.Tech programs. So if your Son achieves good marks in the JEE Mains and also good rank then he can get admission in the top institutes of the India which offer Btech programs such as National Institute of Technology,  DelhiTechnical University, VIT Vellore,   SRM Chennai,  UPES, Delhi University, etc. Also, his main score will be valid in all the colleges of Chattisgarh. But if he wished to write a separate entrance exam for a specific university, then he can do so, as a backup plan.

Thankyou!