Nope! There will be no issue with the present existing BSc degree. The student can complete the graduation as in the 3rd semester. Side by side, he/she can opt for the Biology subject in NIOS and on qualifying he/she will be eligible for NEET/JEE. Now why he/she is opting for the Biology if required to go for the JEE MAINS because for JEE the student require to have Physics, chemistry and Mathematics in 10+2 and there is no need of biology. Is it because of the attempt limit of JEE MAINS, then yeah! technically it may not be possible as he/she have passed 10+2 with PCM in 2019 so he/she was eligible for JEE MAINS for the year 2019,2020,2021 & JEE ADVANCED 2019,2020. Also if the student wish he/she can go for other engineering entrances such as WBJEE, MHTCET, VITEEE etc.

For more information regarding NIOS consider the link below:

https://school.careers360.com/boards/nios

I hope this helps. Wish you a great day!