I have had the flu a couple of weeks ago, i got better and now my left tonsil is very enlarged. i hurts to open my mouth and is painful to swallow.

Large tonsil: The symptoms you are describing are concerned for a possible peri-tonsillar abscess. That's when there is a collection of pus behind one tonsil. It typically causes a lot of pain on one side, it's hard to open your mouth because of pain and your voice will sound muffled. We call that a "hot potato" voice. Once you have the symptoms you are compaining of, you really need to have this evaluated.