Hello there! 

Greetings! 

No dear, you cannot join in NIT/IIT/iits after completion of your three years Diploma course because NIT/IITs does not offer lateral entry admissions to B.Tech course. Only candidates who had completed 12th standard from a recognised board and those who had secured good rank in JEE Main, Advanced examinations are eligible to get admission in NIT/IITs/. Since, you had not pursued 12th standard, being a Diploma holder, you cannot admission in admission in B.Tech course in NIT/IITs or iits 

Diploma holders are eligible to get direct admission in second year of B.Tech through different CET's of state governments.

thankyou