What Causes A Sore Throat?

Hi, I have a sore throat. It hurts even swallowing spit. inside, it's swollen on the left side throat at the very end of tongue when i swallow, my left ear hurts too... on the right side of throat, it doesn't hurt when i swallow but there is some kind of knot i can feel with my fingers when i touch my neck right below my jaw and ear. it's been for 5days now...it is serious thing? should i go to see a Dr.?