How old is your goose?
How long has she had the lump?
Could you post a picture of her from the front and side? I want to get a better look at it.
Could you describe what level of hardnesss it is? Like does it feel like a hard lump of clay? Or If it feels like there’s a rock in there, or does it feel gooey like a bag of jelly?
It’s impossible really to say what it is based on pictures, it could be a lobe, stored fat, which is completely normal, she might not want you touchng it not because it hurts but because she just doesn’t want you touching her there.
Whatever it is only a vet can really say for sure though, some tumors can be removed easily if caught in time, or it could be a pocket of pus from an infection/old injury that needs to be drained.