I Had A Sore Throat For Several Weeks Which Was

I had a sore throat for several weeks which was eventually treated with Zpac. I suspected strep although my doctor never did a swab because it was a weekend. I have been off the antibiotics for a little over a week( I thought I had fully recovered) and now have an irritated spot in the back of my throat. Could it be related? Is it possible the Zpac didn't fully treat the strep. Could it possibly be an STD?