That's a nice old Target model. I can't imagine someone abusing it like that. The accuracy will please you!
I couldn't leave the butt like that. I'd use the restorer's method to get most of the nail head marks out of the grips and butt of the grip frame.
Remove the grips, soak a rag in water, and heat up the clothes iron. Leave the wet rag over the damaged area and apply the hot iron. Re-wet the rag and repeat. this will raise the dents in the wood. Repeat until the wood no long raises.
Pt the grip frame upside down in a vise and with a flat fine file, file the nicks out of the metal keeping the surface very flat, but don't file far enough to remove the serial #! Finish up with 320, 400, 800 and then 1000 grit wet or dry sand piper.
Fine sand the butts of the grips till even with the metal and coat with a wood finish like Birchwood Casey's Tru Oil.
Cold blue the surface of the metal by first heating the metal with a hairdryer, applying four coats of bluing, heating between each coat. It won't be perfect but a heck of a lot better!