Thanks for posting your query here.
I understand you have noticed a small white spot in your gums below your front lower teeth. I advise you go to a dentist
and get your teeth examined. The white spot on the gums could be a sign of periapical infection which manifests as a white spot on gums. Periapical infection could be due to injury
or trauma to your front teeth or it cold
be also because of excessive accumulation of tartar
[calculus]. The dentist will put you on antibiotic course and may advise a xray for the region also suggesting you to get scaling if needed.
Hope that answers your query.I would advise you any day to quit smoking