I'd be afraid to put anything liquid on leather, other than product specified for leather. Have you tried multiple dishes of baking soda, set near the sofa? If other fabrics or rug in room, spray with Febtreeze, or sprinkle baking soda over rugs, scrub in, let set 4 hours, vacuum.
saddle soap to wash it with. the nicotine leaves a sticky layer behind. use gloves nicotine is considered to be a hazardous chemical, and it can be absorbed thru the skin.
I'd be afraid to put anything liquid on leather, other than product specified for leather. Have you tried multiple dishes of baking soda, set near the sofa? If other fabrics or rug in room, spray with Febtreeze, or sprinkle baking soda over rugs, scrub in, let set 4 hours, vacuum.