[LunarBerry]

I've had my old jack russell develop a bump but it got to the size of a large silver dollar within a month or two, and she was very sensitive to it. This was a year or two ago and recently I've seen bumps like the one you showm and they haven't gotten much bigger. With the larger one, we had given her surgery and according to the vet it was a form of cancer, but she seemed very optimistic that it won't come back, just need to keep an eye on it. So I'd watch for an increase in size and sensitivity. but it wouldn't hurt to check or have it removed anyways, just to be sure.