It looks as though it has all crusted over but no official scab. It looks like it has deflated some what today but hasn't gone.
My other chook (silkie) who has been brooding some eggs for the past week seemed fine and showing normal brooding behaviour (quiet, sittting flat, popping off for 10 odd minutes to eat and drink) but when she returned to her nest I noticed about a millimetre of dried red on the tips of both nostrils.
I'm located in Australia, New South Wales. We are just entering spring and averaging 23 degree days.
Complicates things for me to be able to suggest since I'm not sure what you can get there though... if you can find something called Denegard (Tiamulin) without having to get a prescription, it's an antibiotic that helps with MG type issues without having withdrawal for consumption of eggs... it has no relation to human antibiotics so is safe...
I don't know what else to suggest for your hen, sorry... but might try a warm, wet compress on the chicks lump area to remove the crusting and see if there's any type of hole to the infection inside... it would look yellowish or whitish... otherwise you would need to get a nice sharp and clean razor knife to make a small incision to get to it... if it's full on infection it may never heal properly without being removed...
~ So Dark the Con of Man ~
"Man is not what he thinks he is, he is what he hides..." ~ Andre Malraux