Rough textured finish

[jbl11]

Hello everyone,
I've just filled in a hole and sanded it down. Now trying to find the right finish.
It looks like a matt emulsion, but it's almost like it's had something added to it. It's a very slight texture, that you can hardly see but it's definitely there. So my patchwork sticks out because it's been sanded smooth.
Is there a practice of adding something to paint, perhaps to hide imperfections? I've looked at textured paint, but it's far too much of a texture.
Any ideas please?

 

[jamin]

sharp sand maybe?

Failing that light sand and repaint the whole affected wall.

 

[ironsidebod]

Are you sure it isn't the stipple created by a roller?

 

[jbl11]

I was thinking that at first, but dismissed it because it looks the same around light switches etc, where there are obvious brush marks i.s.o a roller.
But I will give it a go with a roller. Maybe the stipple from the roller would be enough to make it un-noticeable. Failing that, I will do as suggested and sand the whole wall - I prefer a smoother finish anyway.
Thanks both