It reeally hurts to swallow!! HELP!?

The back of my throat is sort of red and the left side, and when ever I swallow (and yawn) it hurts soo bad! It was like this a few days ago only on the other side and no where near as bad. This is so bad, at first I thought I might have a cut back there from eating something so I gargled salt water but it didn't hurt at all so I'm guessing threres no cut, it feels like a sore muscle would, a reeally badly stretched muscle that it, its terrible! What could this be