hii 

you have a prety managble rank where as it depends on the branch you are intrested in where as you have great chances of getting NIT but i would like to suggest you to go through the link which has a cut of all the NITs so that  you can decide which branch and NIT you can get fit in along with that you can even try for the college predictor which gives a great results

https://engineering.careers360.com/jee-main-college-predictor

https://engineering.careers360.com/articles/jee-main-cutoff

regards

hello 

at 18701 rank in jee mains and st category you can surely get seat in good nit colleges. you can predict your colleges as per your category and rank at https://engineering.careers360.com/jee-main-college-predictor. feel free to ask any doubts in the commentts section.

hope it helps.