Does smoking directly cause lung scarring? Quit after 25 years mild scarring left low lobe no asthma or COPD what is probability scarring will stop?

Scar is permanent. Scars are generally permanent. Smoking causes injury which goes on to heal with scar. Given the level of anxiety that you re experiencing over this condition, i would recommend that you schedule a consultation with a pulmonologist to fully answer your questions and allay your fears.
Good news. You quit and there is no reason for scarring to continue. The left lower lobe abnormality should also disappear. Your smoking was not too bad, compared to heavier smokers.