Sore throat one side but no cold or infection or virus ? what is this ?

Maybe viral.: What makes you think you have no virus infection? A viral infection of the throat occasionally hurts on only one side.

Throat pain: In light of your age the most like dx is viral or bacterial tonsillitis or pharyngitis. Infections can affect one tonsil more. A peritonsillar abscess can also develop and you should seek attention immediate attention. Sometimes acid reflux or other problems can cause this. If it doesnt improve in 8-12 days or if it gets worse you should see someone.