During tonsil treatment new sore behind uvula and small white & red dots on left side of roof of mouth. Only left tonsil infected. Actually mono or reaction to meds like sjs blister? Chills nofever

Tonsil lesions. You might have a viral infection on top of the bacterial one. I suppose you have been on antibiotics for the tonsil infection. I would watch the mouth lesions and finish the antibiotic. Gargle with warm salt water and take Motrin or tylenol (acetaminophen) for pain. Good luck.
Otolaryngologist. Mono usually affects both tonsils and a routine throat culture checks for strep. A viral infection like herpes is a possibility. Sjs(stevens johnson syndrome) doesn't sound likely. I recommend an evaluation by an otolaryngologist for diagnosis and treatment.