You're actually doing an open jaw (outbound BOS-ITO and return HNL-BOS) on AA and buying a separate ticket to close the open jaw (ITO-HNL). There's no rule against it, and people do it all the time.

Even nested tickets are perfectly fine. The thing airlines don't like is when people use tickets out of order specifically to avoid minimum stay restrictions that would otherwise require them to purchase more-expensive tickets.