if you are a smoker or have other risk factors cancer of the throat is always a possibility but with a sore throat for only four days -- one that is strep negative -- the most likely culprit is a plain ol' respiratory virus. these viruses tend to last a week so hang in there a bit longer. if your sore throat persists consider getting a blood test for mono and/or see an ent for an exam. if you are a smoker. stop smoking.
i've had a sore throat for 4 days and it is not strep with no other symptoms could it be throat cancer