What could be causing the foul taste in the back of my throat?

A couple weeks ago I had a sinus infection, and like with every sinus infection, there was a very foul taste in the back of my throat. Normally this goes away, but this time the sneezing/coughing is gone, but the taste is still there. It's not even really a bad breath type of thing, it's just when I swallow really hard, occasionally clear my throat, or drink certain flavored drinks, the taste comes up. There is no green phlegm coming up like normal with a sinus infection. In fact, and sorry if this is gross, but I can put my finger all the way in the back of my mouth, and the smell isn't on my finger, but the taste in my throat is still there. What could be causing this?