I'm recovering from flu no longer have fever. my throat feels like it's being cut open by a knife. is this left over illness? should i go back to dr?

Not Necessarily: If you continue to get better and the sharp pain goes away you can skip a return visit. I believe, though, that your peace of mind is worth the trouble of a followup if common sense inclines you in that direction.

Throat pain: If this started after severe coughing or severe vomiting, then you should be seen right away. Otherwise, it should improve in the next few days. Use an over the counter numbing spray for your throat, or cough drops. You can also gargle with warm salt water to sooth the throat tissue.

Recheck: This is not a normal after effect of the flu. You may have acquired a secondary bacterial infection while battling the viral infection. Certainly, get rechecked. I would also advise the following: warm water gargles, Cold-Eze ( zinc) lozenges and dark brown honey with or without tea. Use Tylenol (acetaminophen) for pain as needed.