You can find a lot of information on all things quitting cigs and
starting to vape here.
From the post:
"
1. Mouth Ulcers
The Quit Ulcers are a common symptom of tobacco withdrawal, affecting many quitters. The ulcers can be very painful, but there are effective topical treatment gels. It has been suggested that high-dose vitamin therapy may also be effective.
The ulcers or gum inflammation may start a week or more after tobacco cessation. They generally clear up after a few days or weeks.
It may be possible that nicotine being absorbed through the mouth can also exacerbate this, as folks using nicotine gum have experienced these mouth sores although it would need to be shown that those using nic skin patches did not suffer so commonly.
It may be that after ecig use, at first, drinking something to rinse the mouth out may help. This will get the nic (or perhaps flavorings or other materials) out of your mouth and not give it a chance to sit there and irritate your mouth tissues and make any sore worse, if this is in fact an issue.
Admin note
Note that PG is a bactericide and virucide, and used medically for that purpose, so that it is more likely to improve this type of symptom than worsen it. It is unlikely that ecig vapor from an e-liquid with PG in will affect the Quit Ulcers in any way except beneficially.
However: Cinnamon flavoring in an ecig refill is known to cause or exacerbate this problem in some people."