Unknown bump

[Littledinostaurs]

I was at the chicken pens checking on them and it caught one of them and it turns out that it has a large look bump at like the middle of its breast bone and I don’t know what it is anyone have any idea

 

[LaFleche]

Sounds like a breast blister to me.

Breast Blisters in Poultry - Poultry - MSD Veterinary Manual https://www.msdvetmanual.com/poultry/miscellaneous-conditions-of-poultry/breast-blisters-in-poultry