Take a few pictures in which the objects at the edges are at the same measured distance from the lens as the objects in the center. (The objects will form a slight arc.) If the center is still inn focus and the edges are still blurry, it's a bad lens (or a bad CCD) and covered under the warranty.
If not, it's a matter of learning how to use depth-of-field. With a wide open lens, the distance from nearest focus to furthest focus can be a few inches, so with one person standing behind another, one can be in focus and the other one out of focus, even if they're touching. (The closer you get, the more the effect - in really tight close up photography, you may have good focus over only a 0.1mm range or less. If you take a picture of 2 mountains miles away and a mile apart, the chances are that they're both in focus, because, as far as the camera is concerned, they're both at an infinite distance.)