help

hi i bought a google nexus 7 for my son second hand, he has factory reset it and now it wont start properly....it loads to a welcome select language page then diverts to settings and we cant go any further..... i should add that the previous owner has switched the device from android to something called miui which i think seems to be the problem as a mi.com logo appears before it goes to settings. can someone please help as i know very little about these devices.thanks.