Siri thinks I am someone else!

When I first got my iPhone 5 and began using Siri, it called my by my nickname, which is fine. In the Contacts app, it shows my name in blue with a facebook person silhouette next to it. Fine, I thought, it recognizes who I am. Great.

Now, however, I don't know what I've done, but Siri now calls me by a different name. In the Contacts app, it shows that other person in there highlighted in blue with that silhouette; my name is no longer highlighted. Thus, Siri now thinks I'm someone else.

How do I correct this issue?