I had an abscess on right tonsil. Given clyndamycin. Both sides of my throat are still really sore. What could this be?

Ask your doctor. You may need imaging studies and culture of your throat and other areas to determine what is going on. The best person to consult with is the doctor who prescribed clindamycin. This may or may not be the best drug depending on what is going on. Good luck and hope this gets better soon.