Hi Sharon,
I have had in the past swelling in the same area you have. The first time I headed straight for the Emergency Room after calling my Doctor in a panic. It ended up being a blocked Salivary Gland and the swelling went down in a couple of days. Massaging the are helped a lot. This has happened a few times now and I think I have pinned down the reason for it. I seemed to be suffering from extreme dry mouth every time and no amount of water/liquids seemed to help alleviate it. Mix this with something like a Burger or some kind of sandwich and you have a blocked gland. If you think back to what you ate and how dry your mouth was that day I bet that is what has happened to you.
David