I honestly don't think
Aaron needs a nn. It's not like everyone bears it so they need a nn, it's not long and doesn't have an obvious one eg. someone called
Samuel will eventually be called
Sam by someone, whether he asked to or not.
(apologies if any are repeats)
RonA initial eg.
Aaron James could be A.J.
AriRonnyAz
Erin (only kidding)