Be sure to use water when you sand it too. The finer grit paper will clog up fast if you don't. Just work slowly and carefully. You can do this in a sink, with the water running slowly, or just soak and re-soak the paper in a dish with water. Once you get the area smooth, you might want to lightly respray the same color over the trouble spot and be careful not to mess it up this time!
Sometimes, if you have a fine enough grit paper (like 1500 to 2500 grit), you can polish the trouble spot smooth and then hit the whole body with a little clear coat to remove any trace of a mess up.