It may happen to stain a wall, in these cases you can clean with a sponge.

Where it is not enough, the stained part will be sanded with a lightly padded sandpaper and then retouched with a brush.

Remember that if you do not use standard colors, but colors made specifically, to keep in a glass jar a bit of color just in case of these tweaks.

If you have not retained touch-up paint, you can recreate the color by keeping the tint-meter code (machine to make colored paints.