Can you move it around, like it is just in the skin, or does it seem to be attached to something underneath the skin? My springers, when they were a year or so old, started getting what I called fatty lumps. They were hard, but I could move them around with their skin. The vet said they were nothing to worry about and the older they got, the more of them they had. Our female got smaller, hard lumps that had to be lanced and drained. I would call my vet and describe it to them. It is probably nothing, but I would want to be sure.
Kathy