What is this on my hen ?

[Arnab Farm]

I have noticed this pimple-like thing growing on my hen does anybody know the cause and how I can fix it?

 

[azygous]

For your photo to be viewed closeup, select the "full size" option.

Even still, you will need to supply additional info so we can fill out the third dimension. Is this lesion rock hard? Soft and spongy? Palpate it and try to move it laterally to feel if it is rooted below the surface tissue.

How long has she had the lesion? Did it just pop out very recently? Has it been growing for a while, and how long?

How old is the chicken? What are her origins? Feed store/hatchery or private breeder or hatched in your flock?

Look inside her mouth for any other such lesions. The inside should be smooth and pink.

 

[TomNY]

The first thing that came to mind was "tick".