Maybe he enrolled in a masters program. As I mentioned in another thread, he just has to be enrolled. I don't think they check if he is actually attending. And those physical culture institutes are very lenient to elite athletes.
If he entered masters program, he would not be named like graduates only, no? This year he came back to Moscow, there were articles about it, Nikita was mentioning his army duty, no word about any study... somebody mentioned that in his facebook or somewhere he wrote that he finished University in 2013, nothing about Masters.
As I know most of Universities - you study them for five years to get diploma, if somebody wants to continue studying after getting diploma, those people usually stay at University and are doing some work and learning young students (so Nikita should have his own class and give lessons to them every week), those people are really present at University for whole year.