Battery Issue or worse?

I just went to use my macbook and couldn't click on anything. The button was stuck down. I read somewhere to stick a piece of paper underneath the bottom bar and slide it back and forth, "flossing" underneath it. This didn't work, so I took the battery out and realized that it worked just fine with the battery out. When I put the battery back in, I could see it pushing up against the bar and realized that was my problem, can i fix this? Am I doing something wrong? Is this a common problem to have?

Is it new or still under warranty?