Small wound-like cut on lower jaw?

My cat was diagnosed with hyperthyroidism 4 years ago. 

2 pills a day, she has been fine. No signs of pain, Very good spirits

In less than 2 days, a small circle cut has appeared under her jaw. Tomorrow she goes to the Vet,maybe Wednesday.  Any ideas if is related to hyperthyroidism? 

We have a sometimes aggressive male cat that occasionally likes to take a swing a one of our 2 females, but i am inclined to think it was not him.  Being summer, we just treated our small dog  for fleas. Could it be a parasite sign for my cat? 

I have no idea what it is, except I doubt it's anything at all to do with her hyperthyroid.  Let us know what the outcome at the vets is.

Could be ringworm. It is highly contagious. Cats can pick it up outside just from infected dirt. Humans can get it from cats too as well as cat to cat.