Dear Scott,
The only way to know for sure is to have it looked at by someone, preferably an otolaryngologist (ENT). If there is anything there to scrape or biopsy and send to a pathology lab to be looked at under a microscope, that is the specialty that does that.
Even if you are lucky this time, you may not be so lucky next time. You don't want to be here in a few years writing another note that starts with "they saw a spot on my chest x-ray. If anyone has had a similar experience and can shed some light on this issue, please do." I mean this nicely - Quit now.
-Amnia
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Several readers may not know what "dipping" is, so I have included some information below:
Dipping Tobacco
Dip is commonly confused with chewing tobacco. Instead of literally chewing on tobacco, a small clump of dip is 'pinched' out of the tin, and placed between the lower or upper lip and gums. The dip rests on the inside lining of the mouth where saliva carries nicotine to the inferior or superior labial arteries.
It should be noted that dipping tobacco, along with most tobacco products, has been traditionally identified by the medical community as a cause of cancer. The risk of mouth cancer is significantly argued by some American public health professionals, as noted in several recent and past studies.
Smokeless tobacco contains nicotine, which is the primary addictive agent. Warning labels for smokeless tobacco sold in the U.S. include:
WARNING: This product may cause mouth cancer.
WARNING: This product may cause gum disease and tooth loss.
WARNING: This product is not a safe alternative to smoking.
(excerpt taken from Wikipedia)