i m getting 125 marks in jee mains 2020 8 january shift 1 can i get a decent nit

As of now it is very hard to predict your rank/percentile. It keeps changing every year depending on the students' performance. So we'll have to wait for the official result declaration to make any kind of conclusions.
You may look at the previous year cutoffs to get an idea:
https://engineering.careers360.com/articles/jee-main-cutoff

Hi Sanskar.

It all depends on this year's cut-off, but considering last year's cut-off, you will not be able to get admission into any decent NIT if you are of the General Category. The cut-offs this year won't be very different because after reading the current analysis of the January 8th Paper 1 by Resonance Institute, Chemistry was easy, Physics and Math were moderate but Math was lengthy.