hello supratik,

I think you can not take admission. The Diploma Degree holders are not eligible for admission to NITs/CFTIs after qualifying Mains. They must appear in JEE Advanced 2019 & qualify it to become eligible for admission to Engineering Programs. for more detail about jee main click the link and read full article-

https://engineering.careers360.com/articles/jee-main-eligibility-criteria

Hope this is helpful for you.

Thank You.