I'd definitely see a doctor. Same thing happened to me not long ago... except about 4 or 5 days later I got a terrible inflammation on my tonsils and couldn't swallow for a couple of days - tonsilitis. I took some antibiotics and about two days later it cleared up. You could have strep, mono, or any other viral/bacterial infections. A doctor can help determine what the problem is and cure it in a couple of days.