Bump on back of head Help !

[Roxana72000]

Hey I have an emergency as one of my Brahma hens got a huge ball at the back of her head I thought maybe the rooster hurt her and it would go away but it’s been a week or more and it’s still there I see it getting a bit bigger and now leaning to one side I don’t know what to do their is no other signs of sickness just a big ball

 

[Eggcessive]

Does the area feel soft like a leaking air sac, or swollen like tissue swelling? Is there any scratch or cut?