looks like an abcess to me, too. i had 2 goats that used to get them occasionally. the vet would come out and lance them. nasty though, it looked like runny cottage cheese. bleh! not serious though, just ugly. best to have it treated. if it bursts on its own, which it will if it's a simple abcess, it could lead to infection.
Yes I was thinking that is what it might be. I had a Nubian goat that had it. She didn't get too many cysts and she lived to be 13. Since you don't have any other goats I would give it some time to see how the infection progresses. If it decreases the quality of her life then you may need to let her go to rainbow bridge. Keep your chin up, it might be manageable also.