Are you just needing to do some photo editing then? Like you are wanting to have the (what im guessing) tiretracks continue through without the extra smudges?
I’m also guessing you are trying to make it into a tileable-texture?
I think you might have a bit more luck posting texture\image\decal related questions on maybe a Blender forum, or maybe GIMP.
Here are a couple free texture creation utilities…if this is what you are trying to do.
Modlab
Materialize
http://www.boundingboxsoftware.com/materialize/index.php