Answer:
You probably have tonsillitis.
Although we have two tonsils, it just happens that your left tonsil is sore.
Go to your doctor for help.
I can recommend oral lozenges such as Strepsils for you to take..
And probably your doctor will prescribe you a very strong form of antibiotic with a generic name of Co-Amoxiclav.
You cannot buy thiis without prescription..
So, just take Strepsils for the mean time and see the doctor soon.