That's probably a good thing, I'd act on it if you want to come to Columbia.
For everyone who was waitlisted, don't hesitate to send updates or a letter of interest/intent to let them know you still are interested. I've spoken to Dr. Nicholas in the past about letters of intent. While they don't particularly like it, they do take LOIs with the assumption that financial aid could still be a deal breaker. Most waitlist movement occurs in May and beyond, so it is best to get anything you want to get in before then. You can request a second interview with Dr. Nicholas (by phone if you aren't near by) if you did not interview with him before. You can still correspond with him if you did, just not a formal interview.