Sore throat for one week?

I have a sore throat for one week. It all started last Wednesday. I started using mouthwash for throat. This helped and by Tuesday everything was ok, Today i have a feeling that is coming back. I didn't have any other symptom like high temperature or any kind of temperature, cough, swollen nodes... only other thing that in the morning my nose i little bit full but i can still breath on it normally. What could cause this problem of mine???