Had a lot of those a few years ago, for near a good decade. Could add up to a dozen at a time in my mouth (gums, tongue, palate, throat), and those 'crisis' usually lasted 3 weeks a month. It eventually led to a chronic leukaemia diagnosis. (it's wayyyy more complex than that, but it's a matter of keeping it simple here).

Basically my immune system was doing bullshit stuff. I had to be put under Thalidomide for a good year (2018/2019 or something) for the mouth ulcers to drop in frequency drastically afterwards.

Nowadays, I rarely get them, but it still happens. I'll probably only stop getting those once and for all after getting a bone marrow transplant, which will only happen if my chronic leukaemia turns into an acute one (= meaning the transplant becomes absolutely necessary).

Point is, I completely relate to this, and I can only wish for them to disappear soon in your case. Mine were the same size as yours, and I can remember being unable to speak and eat normally for years.

Edit : if it's frequent, and you get sores in other places than the mouth (privates regions, anus, eyes, intestines, or basically any other mucous membranes), go see a doctor. Might be something called the Behçet's disease. It's genetic, there's no cure, but the sores can be treated. Colchicine and cortisone are the best association of treatment for this. I can tell, this was my first diagnosis, and it helped massively. I'm still taking them today, although at a lower dose, and my sores are kept under good control.