Possibly a Canthigaster Jactator, but again I don't know where it was caught or have much to go off of. It's endemic to Hawaii so. Actually looks like a boxfish.
Also possibly a black spotted boxfish.
A more detailed pic is 100% necessary for me to make anything more than a guess.
Display tank - 24g nano w/ softies/montipora
I run electrical appliances underwater and enjoy injecting things with Kalk filled syringes.