Considering that its so shallow, you can avoid fillers totally.
Just stick a sheet of fine grade (220 grit is good) wet dry sandpaper on a nice, flat, smooth surface such as a sheet of glass or plexiglas. Put a few drops of water on the sand paper, place the flap, pin mark side down, flat on the sandpaper and keep even pressure on it while moving it around in a circular motion on the sandpaper. Check it frequently to guage your progress.
Once youve got the pin mark out of there, you may want to repeat the above process using a couple of finer grades of sanding film to give it some polish.
In the case that the flaps are molded right into the wing instead of separate, pay a visit to the nail care section of your local drug store and pick up a selection of nail buffing sticks, they're usually larger and wider (not to mention cheaper) than the specialized ones you get at hobby shops. You can get them coarse enough to remove your offending pin marks and fine enough to get a nice smooth polish back when you're done. No one will know anything was ever there.
All you have to do after that is restore whatever surface detail got sanded off and you're free to carry on.
Save your fillers for more worthy applications :-)