Actually, no, not really. "Ain't nothin'" belongs to African-American English, which is not just a "wrong" dialect of English.
Interesting...
You see, I'm originally from south west England, where, as you might imagine, there was a real shortage of African-Americans, but there was a wealth of people who said "ain't nothin'".
When I was at school, our teachers did their utmost to educate anyone who said "ain't" out of it, frequently lecturing us on the evils of the double-negative.
Chris
