Is it very difficult to get admission in IIM Nagpur?

Your question is quite vague given that the admission criteria are directly linked to your profile. The chances of one’s admission are proportional to your grades and experiences and therefore cannot be generalized. 

Let me elaborate for you. In the entrance exam, every candidate has their own strengths and weaknesses. One might be good in the Quantum section but as at General Knowledge and vice Versa. While many get good scores in the entrance exam, they fail to muster the courage to speak in the interview which lowers their chances of admission despite a good CAT percentile.

Still, if I rate the level of difficulty to get admission at the top IIM A B and C as 10/10 then I will rate IIM Nagpur as 6. This is because I know a friend who scored 92 percentile with decent past academics and work experience of around a year and yet got into IIM Nagpur.