Smirch -

This is the literal dirt, soot, or grime that soils a surface. Think of a muddy smudge on your clean white trousers or a blemish made by dirt on a pristine wall.

Dealing with a smirch requires a quick response and the right tools. Here is how to scrub away the damage: smirch

(verb): To make something dirty, stained, or discoloured. Smirch (noun): A stain, blot, or blemish on someone's reputation or character. This is the literal dirt, soot, or grime