Although Canker sore does occur quite frequently on the tonsils, an ulcer in the mouth or throat shoudl always be examined by an ENT specialist to rule out any maliganay and to confirm that uit is indeed a cancer sore.
Canker sore is usually the result of an infection or a trauma by hard food or by an allergic reaction to food or medicine.
In your case, it is likely that you gat an infection earlier which has now devloped into a cancker sore.
Most canker sores heal spontaneously in 1- 3 weeks although larger ones can take upto 4 weeks.
To encourage the sore to heal early and to prevent infection, please use a mouth wash containing Chlorhexidene, available OTC, for gargling - chlorhexidene is a very good oral antiseptic and will help to keep bacterial infections under control. Warm water with 2 tsf of salt mixed in it is also a good mouthwash.
Drink plenty of water - at least 8 glasses daily to keep the mouth clean and moist.
Take Motrin 500mg twice daily after food for 7 days to decrease the pain and inflammation.
Please get an ENT checkup as early as you can.
I hope this helps.
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