"bubble" growth on 3 week old barred rock chick

[sodinedia]

I noticed it a few days ago, and now it seems to be getting bigger. I'm keeping her and two other chicks in a brooder inside our garage, which we keep clea. Did not notice it when we bought her at 4 days old. anyone have any ideas on what it could be?

 

[Eggcessive]

I haven't seen that before, but I wonder if it might be a little abscess or pus filled bump from a peck wound? I would be tempted to gently lance it with a sterile needle, and gently squeeze out contents, then put a small dab of Betadine on it (cleanse with the Betadine before lancing with a QTip.