Hey Kalpana.

Various law colleges have their own guidelines and rules for admission. The eligibility criteria for admission in most colleges for law after 12th class is a minimum aggregate of 45% marks in 12th. Some colleges do accept 12tg from NIOS board where as a few colleges accept admissions only if 12th class is foen from a regular board. Hence though you will be eligible to take admission in a few colleges after 12th from NIOS, but you will have less options. And there might be a change is policy by Bar Council India or law colleges in future regarding this which can't be predicted. So it's better to be safe with regular boards in 12th. Otherwise as of now NIOS in 12th is accepted in various colleges.

Best of luck