I'm a Nigerian highschool student currently studying abroad, and I'm interested in programming. I may be visiting Nigeria in the near future and was wondering if it would be possible for me to represent Nigeria in the IOI, and how I would go about that as there is very little information available online regarding the application process.

If you have the skills, why not? Your main problem would be the overly bureaucratic process around these things here (I suspect you are also American). Most of the time it involves paper applications rather than online. Add that to the inefficient process we have here (and discrimination you'd face for not being a "real Nigerian" it can get frustrating. I'd advise you start at the ministry of education and ministry of communication (IT is under Communication ministry)

They select people from the national Olympiads they hold so maybe you could look that up.