i got 70percentages in jee in bc-a category can I get any seat in nit

As per your percentage it is hard to get admission in NIT , you can go for privet colleges in india, and also you can try your home state NIT,

And also you can show the low NITs  as the cutoff

You can see this link for cutoff the NITs in different states
https://engineering.careers360.com/articles/jee-main-cutoff

But I Suggest you as per you rank privet college is best for you.

You can visit here the top privets college in india
https://engineering.careers360.com/colleges/list-of-private-engineering-colleges-in-india-accepting-jee-main

You can also try for government colleges in your states .

And also predict your rank and college from below link

JEE Main College Predictor link
https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer

JEE Main Rank Predictor
https://engineering.careers360.com/jee-main-rank-predictor

Thank you i hope this answer help you.