Answer : The qualifying word is "architect". Interior design, on the other hand, is not a profession with clearly defined requirements. I'm certain the OP enjoys design work and can pursue it in conjunction with architecture, but they should be very careful before labeling themselves an interior architect.
While they may have studied fields such as color theory or graphics software along the way, to become an interior designer you will need to gain some outside certification or demonstrate proficiency in these areas through your portfolio. This process could take from three months to two years depending on how you track down these certifications and education opportunities. Remember that there are wrinkles that arise all of the time in regards to licensure; this article covers many of them wonderfully.