No. Need not worry. That just mean you are protected. You have the antibody against hepatitis b!
Not necessarily. Your body makes hep b surface antibody in response to the hepatitis b vaccine. It can also make it to the hepatitis b virus. If you've been vaccinated, it's more likely to be due to the first reason. If you're still concerned though, a test for hep b surface antigen and a liver function panel should clear things up. Most likely, they were checking your immunity status.