Hello, I know that is very stressful for you both.
However, I couldn't even begin to comment on what this lesion may be. None of here are Doctors. We are Oral Cancer Patients, Survivors and Caregivers.
Please stay away from Dr Google and all the misinformation there.
Either make an urgent appointment with an Oral Surgeon, or an Otolaryngologist. You don't want an ENT Dr who just does grommets for kids.
As your Husband has had this lesion for longer than 2 weeks , he needs to have it biopsied. Only a biopsy will tell you what this is.
Good on your Dentist for commenting on this lesion and recommending further evaluation.
I wish you the best and hope that this turns out to be benign and nothing to be concerned about.
Tammy.

Caregiver/advocate to Husband Kris age 59@ diagnosis
DX Dec '10 SCC BOT T4aN2bM0 HPV+ve.Cisplatin x3 35 IMRT.
PET 6/11 clear.
R) level 2-4 neck dissection 8/1/11 to remove residual node - necrotic with NED
Feb '12 Ca back.. 3/8/12 total glossectomy/laryngectomy/bilat neck dissection/partial pharyngectomy etc. clear margins. All nodes negative for disease. PEG in.
March 2017 - 5 years disease free. Woohoo!