Removing Tar Marks from Fireplace wall
Tar can be removed with a product called TAR-X sold for this kind of thing and similar products from auto stores for removing tar from autos near paving projects.
From the location, it sounds more like a creosote problem. This should not occour interitor so an inspoection by a qualified mason or chimney sweep is called for in that case.
If it is just soot, a vacumn and scrubbing can handle it.