Hello Jigmey,
It is not mentioned anywhere on the college website that NIOS students cannot apply for the Journalism course in the college. So ideally you should not face any difficulties as NIOS is valid and equivalent to the rest of the boards such as ICSE, CBSE, and State Boards. What you need to remember is that you need to have English as a compulsory subject in your +2 level and the marks requirement for application is 60 percent aggregate (English + Any 3).
In case you have further doubts you can contact the concerned department at  9133-2255-1207

Hi Jigmey,

There is no issue in getting admissions in St.Xaviers Kolkata if you are a NIOS student.NIOS is a well-recognized board as CBSE or ICSE.You can seek admission in any college you wish for; they'll accept you.

Hope this helped you.

Thanks!!