a smooth sand, spackle and paint.

Thank you- on the upper step, do you think it appears ubrupt to have the end of the baseboard like that? I keep thinking about the transition of floor and step to baseboard. Possibly using quarter round. Not sure. thank you for your comment

no quarter round.

a better photo of the whole area could help with a simple fix.

'the big picture' how does it relate to the whole space.

Do you need a larger Base/Trim?

thanks for the input. That would make for a clean and simple end and could repeat on the next step. Basically, no verticle base board being forced to tie it all together. thanks again.

Paul F, that's an interesting approach. Thank you. And then repeat on the step?

these two images seem to have vanished, so putting them here.

I don't have baseboards on my stairs but in your situation I'd use put one, but stop it short, right at the seam where the bullnose plank was added... 2-3 inches short of the edge of the stair.

Run a piece of baseboard vertically, mitered at top (upper baseboard would have to be extended), coped at bottom and nosing? Not as simple, I know . . .

Or mitered top and bottom, with a corner cut out for the nosing (miter cuts shown) . . .

Mine had something like this, although I did convert it to skirts, because in my case it seemed a little cobbled, but it can done well

Or like this, a small piece that could tuck under the nosing and trim any gap on the tread.

For the nosing, you could play with a hole saw followed by a jigsaw and some sanding. I don’t know how well that would work. You could practice on scrap baseboard if you are interested.

Or if you are bold, you could consider using a dremel to chip out a bit of the bullnose so you could slide straight baseboard in there. You might have to patch, sand, touch up stain and poly afterward. Again, I haven’t tried this yet so I don’t know if you’d have a satisfactory result. It may mess up your stair edges.

Another option is to remove some drywall and replace with some sort of wainscoting. That would give you 1/2” of depth to work with. You could trim out above, and just have flat painted wood flush beside the step. But then you would have to design cohesive trim for the entire area.

None are easy options. Figure out what look you would like. Right now the pic simplynatural posted looks best to me, but it bothers me that the left side of the stairs is not like the right. The plain drywall might look good if you can remove the upstairs baseboards on both sides. That’s why I’d consider wainscoting or vertical trim on that upstairs area. Or the downstairs area. Some repetition of whatever design you decide to use.

Thanks, I get what you're saying and defintiely that the left and right are different doesn't help. Since the house is a simple ranch/mcm design, I don't think I'll introduce a new surface such as wainscotting, but good idea otherwise.

I sure appreciate everyone's input thus far. It's given me new ideas to consider, for sure.

I think that although this is more trouble, it would look good...

It needs a skirting board. 100%. Even if small, it needs it.

I made sure that all my skirting died into the baseboard in a smooth line without a step or jump at the top or bottom as it transitioned to the base. Even more work, but clean-looking.

I just googled ”how to add a skirt board to finished wood steps” and got a bunch of videos. Take a look and see if any of those methods are good enough.