Patch stairs?

[mozar]

Hello,
I recently pulled the carpet off my stairs and there are a lot of issues with them. Is there something I can do about the gaps without replacing the entire skirt board? Several of the gaps are quite large.

[NoVa]

I put oak quarter round across the treads, but not the sides, in my house.

Edit: I would probably just caulk and paint the gaps near the wall.

[NoVa]

If the gaps are too big for caulking (a bit hard for me to tell) I have seen old-time carpenters use Bondo to fill gaps and replace rotting wood when they didn't want to replace the piece.

[EricEng]

Giant tub of Drydex maybe?  Should be able to smooth it as needed.
https://www.dap.com/dap-products-ph/drydex-spackling/

Although I think caulk would be a safer choice as it can flex a bit which stairs tend to do as seasons change.

[mozar]

I realize now that I didn't explain my issue well enough. I had  holes in the wall next to the stairs. I decided to use spray foam and then I'm going to spackle over that.