Thank you for providing a picture of Pickles and her bump! It is quite large in the picture, and it could be a tooth root abscess. It could also be an enlarged lymph node, a benign tumor, or a malignant tumor. This is definitely something that needs to be checked out by a vet. It looks very swollen and it likely bothers her. The vet will be the one to diagnose what is causing the bump and the best treatment for it. I would take her into the vet first thing Monday morning. Tonight, I'd recommend feeding some canned food to her just in case it is dental problem and it hurts for her to chew dry food. You could also soak her dry food in warm water to soften it up. Good luck, I hope this helps!