Best way to fill this?

[RockLock92]

What’s the best way to fix this?

[msellers]

I am definitely no expert, but I can think of 3 fairly simple options. First being, you could peen the butt to make it bend slightly filling void. Second, solder a thin piece of brass and fill and fit the brass shim to the wood filling the void. Third and probably the best option, take a sliver of wood from somewhere hidden and make a wooden repair to fill and hide the void.
I am sure more expert people will be along to give better advice.
Mike

[Daryl]

Mikes suggestions both sound good to me.

[alex e.]

I think he might mean the chip at the heel of the buttplate.

[RockLock92]

I think he might mean the chip at the heel of the buttplate.

I do. Apologies for not articulating my problem more precisely.

[David R. Pennington]

Looks minute in photo, like finish would almost obscure it. I would glue a small chip of same wood in and sand down when dry. No one will ever know.

[Scota4570]

For the part that is still there, put super glue under it and press back.  Medium viscosity CA for RC model makers is the best for this type of thing.  IF you can get some accelerator, glue, press, spritz, done.

For the missing chip make a chip that fits the boo-boo and has the same grain orientation.  You will want to split out of simmilar maple.  Since the chip split out the grain direction will match. 

IF you can find the missing piece glue it with super glue when you stabilize the  loose piece. 

Rasp or file damage?  From now on when filing or rasping end grain push toward the middle of the stock. 

[Davemuzz]

Looks minute in photo, like finish would almost obscure it. I would glue a small chip of same wood in and sand down when dry. No one will ever know.

I've done this very thing and it's very difficult to see this type of fix.

[Mike Brooks]

Remember to stain the area before you apply any glue. I would stain, put on a dab of super glue gel, let it dry, sand out and move on.

[smallpatch]

Looks small enough to just file it out.