Hi

With the qualification of diploma you will be eligible to fill the application form of JEE Mains examination but if you want to get into IIT or NIT then you are not eligible for admission in them, also to get into IIT you need to appear for JEE advanced examination after qualifying JEE mains but for JEE advanced diploma students are not eligible also IITs/NITs do not offer lateral entry so if you want to get into NIT/ IIT you will have to do 10+ 2.

But if you just want to get into Engineering College then after your diploma then you can get into Engineering College as there are many colleges which offer lateral entry in 2nd year of BTech directly to diploma students.

Thankyou