<p>Ethically, you should tell the admissions office pretty much what you typed in here, that you identify as African, you’re specifically North African (indicate which country/countries), that you thought North African counted when you completed your application and that you recently found out it might not. It <em>might</em> hurt your chances, but it shouldn’t be by too much, not like the ■■■■■ thread where the guy claimed he was already accepted and was afraid of getting rescinded for revealing his lie. They’ll probably even appreciate your honesty.
The best way to communicate is to write a business-style letter (refer to them as “Dear Stanford University Admissions Office:”) and fax it to them at (650) 723-6050. Just make sure you do it as soon as possible.</p>