Thank you for helping this baby.
What are you feeding the baby?
Can you post a picture of the baby and especially the lump/bubble?
This will determine quickly what this could be.
Is the lump there all the time or just after it eats?
I'm going to find the link of another little one to compare. Here is a healthy 3 day old pigeon.
http://www.speedpigeon.com/3-Day_Old_baby_racing_pigeon.jpg
What are you feeding the baby?
Can you post a picture of the baby and especially the lump/bubble?
This will determine quickly what this could be.
Is the lump there all the time or just after it eats?
I'm going to find the link of another little one to compare. Here is a healthy 3 day old pigeon.
http://www.speedpigeon.com/3-Day_Old_baby_racing_pigeon.jpg