What could be wrong if only the left side of my neck and throat hurt?

Probably see your MD: Usually infections such as viruses or tonsillitis involve BOTH sides of your throat. If this has been going on for more than 2-3 weeks, you really should have a doctor examine your throat. This is especially true if you use any tobacco products. It may be something simple, but a sore throat on one side that lasts more than a couple weeks needs to be checked out with an exam.