Is this an ulcer? An infection?

I’ve had infected wisdom teeth on both sides which were originally painful and then got less severe. I rang the doctor and they advised that I get corsodyl mouth wash which I have (they couldnt see me due to lockdown). I now seem to have this yellow area at the top, it was originally on the surface but seems to have gone deeper and now only hurts if I touch it.

What do you think it is? Any ideas would be helpful!