Swollen Neck- Please Help!

[chickybrink]

I have a apprx 8-9 week old chick. For the past several weeks I've noticed she is losing feathers on her neck. She is the only one out of the flock to have this condition. She seems to be continually grooming, scratching, preening. I posted this picture yesterday asking for help. I am fairly certain she is not getting pecked. Today her neck is extremely swollen and I am very worried. I am a trained ER nurse and too me it looks like cellulitis. What can I do? Please help me. This is my son's favorite girl.

 

[AKSanctuary]

This is the same exact thing that my chick has right now. What was it and what did you do to help?
Thank you