What Causes A Feeling Of Blockage In The Throat?

Hi. For the past few days I have feel like something is stuck in the back roof of my mouth, as well as the my throat. It will not go away. Throat is slightly sore, I coughed up one white chunk. I do no see anything unusual in my mouth except for red spots on the roof. I just finished Z-pack for a sinus infection. What is wrong?