Ipod wont boot

Ok so i know jailbreaking is bad and stuff blah blah blah.... but anyways my ipod wont boot, the apple logo pops up for about 6 seconds then goes away then comes back then goes away, this is what happend after my friend decided to go into cydia and delete everything from the packages so im guessing he deleted core boot files or so shat. Ive tried a restore, the volume button trick, but sadly i have nothing.