Ain't is a word. It's a contraction for am not, is not, are not, has not, and have not. In 1706, it was orginally considered a contraction of am not. It wasn't even first used in America but in the early 19th of the Cockney dialect in London, the United Kingdom.
Hope this helps, HAVE A BLESSED AND WONDERFUL DAY! As well as a great Superbowl Weekend! :-)