I lied to my mom

So today after school I decided to go straight home instead of going to the library like I said I would. It's not a big deal right? But now I feel really bad about it, and every time she looks at me I know she can tell something isn't quite right. Did I make a huge mistake by skipping out on my homework just so I could binge-watch that new series? Or is this just way too much drama over one little fib? And what if she finds out the truth somehow...