There are probably several ways to tackle this problem, but I prefer to use the Blemish Fixer that’s available in Paint Shop Pro. The original purpose of the tool may have been to hide facial flaws in human subjects, but I’ve found that it also works well in getting rid of a lot of other little flaws that can creep into photographs. To use this tool, just follow these steps.
From the Learning Center in Paint Shop Pro, choose Retouch and Restore and then Makeover. The Makeover Toolbar will now be available. Be sure that the Blemish Fixer is selected as shown in the first screenshot above. You may need to adjust the size of your brush so that it fits snugly around the flawed area like in the second screenshot above. To do this, you can either change the number in the Size field on the toolbar or use the scroll wheel on your mouse.
After you’ve selected the proper size for the blemish tool, center it over the flawed area of the photograph and click. The ugly smudge in my photo was small enough that it only took one click to fix. If your problem area is larger or if it is in an area with a wider range of color, it might take a few more.