Somthing hard in my bellybutton not lint?

Im 21 for the past few years I have this hard black thing sticking out of my belly button. My belly button is in Innie so u can't really see it. i asked My mom if she new what it was she said it's part of my umbilical cord that didnt come out and not to touch it. but to me that made no sense cuss it would of fell out when I was younger. This thing in there has never really hurt unless i fooled with it. but yesterday my friend poked my belly button for fun while playing around. Now Im getting sharp pains around that Area. Any one kno what this is . I plan on seeing a doctor when I got the money.