What is this hard mass on chicken's thigh?

[Seamus-Sally]

Two days ago I noticed a limp with one of our 12 week old Barred Rocks. Her toes were occasionally curling up and she was walking on her foot balled up. I noticed a hard lump and began soaking in Epsom salt bath with no noticeable change. She is still having a difficult time walking and using that foot. She does occasionally walk flat footed and sometimes with it balled. Any ideas? Any treatment recommendations? TIA!

 

[MysteryChicken]

How does the area feel?

Any sign of a break?

 

[Seamus-Sally]

The mass is firm, the area around feels normal not hot/warm. There appears to be two "white head" looking spots that could end up breaking open but the mass is harder than I would anticipate a puss filled cyst to be. I will try and take better pictures tomorrow after I soak her again.