Just an update. Since my last post, in addition to the small lump on my chin, I had one appear on my cheek and one between my eye and nose. I'm assuming they were acne, since the eye one is gone, the cheek one is near-gone, and the chin one is very small.
The movable lump on my jaw, however, is still there and still painless, still the same size. However, there is also a lump on the other side of my jawbone.