Mouth ulcers are a sign of
vitamin deficiency/ teeth abrasion.
Sore throat could be covid.
These are not side effects of covishield.
Most people who go to take the vaccine, get exposed to a lot of people at the vaccination centre. Hence they contact the infection.
If your symptoms persist for 4 or more days, you should get rtpcr done.
Meanwhile monitor spo2 thrice a day.
Start multivotamin tablets for ulcer.
Smile/zytee ointment can be applied locally for the ulcer.