You have the advantage being there with your hen, so please fill in for us what our senses don't permit us to experience from a two dimensional photo.
Is there an odor?
Is the lump rock hard?
Soft like a fluid filled blister?
Or somewhere in between?
Does she shake her head and scratch at it?
Have you seen the eye bubble and water?
Have you looked inside her mouth? No? Please do so.
Is she eating, drinking, pooping, and behaving normally?