How to fix stairs that have holes from screws
You want to know how to fill the holes? Or are they still squeaking?
Epoxy kneaded putty is a favorite of woodworkers.
If your stairs are wood you should be able to use some wood putty to fill the holes and then sand it smooth once the wood putty is dry. If you plan on doing any staining or painting make sure you get the wood putty that is stainable or paintable.
Yes, Gk, is exactly correct. Wood putty, pressed into the holes firmly, let dry, then sand and it might be need to be done twice. Sand and paint or stain.
You can fill in the holes with wood putty, then repaint or stain the stairs.