What is Dun No?
It is a swift comment simply informing you that you lack any knowledge you have about the situation.
Darnel: ere blud check ma new ting.
Adeolu: ere fam is that fresh.
Darnel: ya Dun No!
Adeolu: I Dun No?
Darnel: Dun No Dun No Dun No.
See clueless, i dont know