You say you still have pus? That means the infection is still there. May be it is not pus - could be super-added fungus infection or granulation tissue looking like pus.
In the circumstances, you describe, it is very unlikely to be cancer. 'It doesn't look sinister' - appearances are deceptive! The only way to rule out is excision biopsy
(sample analysis) / But one may not take sample during infection - for fear of spread.
You should see your doctor again - ENT specialist
, preferably / In the meanwhile, have antiseptic mouth wash/gargling