Cancer is an uncontrolled growth of abnormal cells. It doesn't come and go nor does it stop once it starts. The fact that the sore resolved bodes well.

Some people are more prone to tonsil and throat issues and allergies could very well be a possibility. It's certainly been a heck of an allergy season where I'm at so I imagine it may be the same where you're located. It's prudent, especially in light of your concern over this to be examined by an ENT that is experienced in H&N cancers. The reassurance will be worth the money.

Positive thoughts