Hi. I agree, that is not an abscess. It could be a cyst or even a wart. Keep an eye on it to see if you notice it growing any - maybe even take pics along the way to monitor it. You could also send a pic to the vet now - perhaps they can identify what it is by looking at it.
You might want to try measuring this object to see if it's growing. My kitty has a soft lump under his skin in the middle of his back and it's not bothering him. His vet has been keeping track of its size and it hasn't grown at all. He's had it for years. I'm guessing it's a soft lipoma which is just fatty tissue, which isn't a bad thing. I have those myself.