I pulled of the quarter round and found that there isn't room to simply knock some shims into place. I'm going to have to take the bullnose piece off and place a piece of wood on top of the attached flooring on the riser (see pics).
Looks like I'm going to have to follow Elite's idea and...
I have hardwood running up the stairs of my house, and a few of the bullnose pieces on the edge of the treads are pulling away. The house is only 9 years old (if that matters). What's the best way to repair?
I was thinking of wood glue in the gaps and driving finishing nails from the risers...