The song is probably "Mannish Boy," a Muddy Waters song.
http://www.lyricsdownload.com/muddy-waters-mannish-boy-lyrics.html
If it's not Muddy Waters who did the version you heard, put the song title in AllMusic.com and go down the list of others who have covered it.
http://www.lyricsdownload.com/muddy-waters-mannish-boy-lyrics.html
If it's not Muddy Waters who did the version you heard, put the song title in AllMusic.com and go down the list of others who have covered it.