Hey dear ,

if you have completed your ISC ,passing in all the subjects without getting carry in any subject and also scoring the qualifying percentage for jee then your are eligible for JEE . nios board is valid in jee , so if you have passed in all the subject from NIOS board then there is no problem. So , a certification of passing ISC  from nios in all subjects makes you eligible for JEE. but passing in just a single subject from any board whether it is a state board or NIOS will not be acceptable in JEE . So , you have to pass in all the subjects from a particular board. Hope your doubt have been solved . Happy helping and all the best for JEE 2019.