Hi, Kristi! I understand that feeling at work - I've been struggling with similar, though different, work issues.
Please have the conversation with your boss and do so soon. Bring suggestions/solutions with you so it doesn't just sound like a whine fest (not that I expect you would make it so, but bosses can interpret things in such ways). Was your boss in the initial interview? Is this the person who indicated you'd be working on interior design? If so, ask what the time frame is. Maybe suggest that you may be able to save the company the time, money and hassles involved in working with outside design firms, by contributing this skill of yours. Suggest you attend meetings where interior design is part of the discussion. How well do you know the architects? Can you bring up your background casually in a social conversation? This might make some lightbulbs go off for them.
Try not to "check out" too soon. The best things in life require some effort and some patience. At the same time, don't stay so long that it sucks all that design life out of you. You've got some very important skills that are being overlooked.
Do you have a formal performance review program? Is development planning part of that process? If you can't get something happening in any other way, perhaps indicating you'd like higher levels of training in design, which would show how much you already know, might get the hint through....
I'm sending you butterflies to help guide your next move and to amplify the peace and patience in your heart so you can hang on until you've had those conversations and you know what you want to do next.
Hugs and butterflies,
~T~