It's an inflamed pharynx(backside of your mouth). It has multiple reasons.
Can be because of infection (if it's very recent)
Can be because of lots of gastric reflux (if it's been a long time)
Next Steps
you can take syrup mucaine gel(for pain),
gargle with just warm water(no salt)
tab pantop 40 once in the morning before food.
Health Tips
lifestyle modification for gastric reflux is the key
don't eat too spicy or too hot food.
at least 2h gap between dinner and sleep.