In Pictures: How to Clean and Retouch Old Photos w...
12. Choose the Freehand tool. Select the background layer and carefully draw around the undamaged left side of the mouth. Draw around a larger area than you need as it’s easier to delete pixels than to add them. Now copy the selection, Ctrl-C, then create a new raster layer and choose Edit-Paste-Paste as New Selection.
In Pictures: How to Clean and Retouch Old Photos with Paint Shop Pro