Place a dropcloth on the floor, underneath the spot that requires repair. Tape the cloth into place with masking tape.
Sand the patched area until it is smooth, using a fine grade of sandpaper or a sanding block.
Apply spray texture. If the rest of the wall is sprayed with a texture, repeat this process over the patched area. Do not apply too much texture. It is much easier to add more than it is to remove too much.
Apply Venetian plaster to the wall. If the walls were plastered to give texture, mix a small amount of Venetian plaster in a bucket. Apply this to the wall with a small putty knife in a cross-hatched pattern, working one way first and then in the opposite way for the second pass, to match the pattern of the original texture. Build up the plaster slowly to avoid over-application.
Sponge on a texture. If you sponge-painted the rest of the wall, replicate this technique over the patch. Feather the edges a little onto the rest of the wall to hide the newly sponged area.