Dental Abscess or TMJ?

I'm going to the doctor tomorrow, but I just want to know what you guys think. My jaw has been kind of hurting on the left side where my joint is for the past four to five days. Everyday I wake up and my jaw feels fine, but come 5, it starts to hurt pretty bad and then gets kind of stiff. It's actually giving me a headache tonight too. So, I was just wondering if you thought it was a dental abscess or TMJ? Which I am unfamiliar with both. Or do you think it's something else? Thanks so much in advance!