It could be a dental cyst due to an earlier infection, causing inflammation, which led to the build up of scar tissue, in response to the infection.
If painful on its own, it might be infected and if not painful it would be sterile.
At any rate, if it's still infected or if it's causing you discomfort and pain, it needs to be addressed. It deserves further investigation, regardless.
A had periodontal issues galore and thank goodness a have a relative who is a dental surgeon and periodontist, who did major work around my gums.
I now do "Oil pulling" every single morning before breakfast, using virgin coconut oil and this helps eliminate most toxins and harmful bacteria from
my teeth and oral cavity in general.
It's better than have them sit around and accumulate in an ideal environment for them and gradually make their way elsewhere, causing havoc in my body,lol!
One thing about your recent thyroidectomy, make sure your thyroid function is properly regulated! (See Dr. Barnes Basal Temperature Test online, for self-testing-the golden standard in the past and much more accurate than modern standard tests)
If you have low thyroid function (this can happen even when you take
thyroid meds like synthroid and levothyroixine-which are synthetic thyroid hormones -T4- BTW)
where repair and healing at the cellular level becomes sluggish!
Many imbalances and conditions start from low thyroid function, which does not sound like a big deal at first, but IT IS!
If you have any questions, please post again.