Chicken with hard lump under beak

[Chickens :)]

Hello. I recently had a mother hen who had left her chicks at 6 weeks and went back to the coop. She was eating normally and began laying as well. About 4 weeks later, I noticed a small lump under her beak which seemed to have a hole in it. Any ideas on what it could be? Is it a mite or maybe a piece of corn caused the problem? It is hard and is the same colour as her beak.
Thankyou!

 

[frostic]

is that a rhode island red? mine have these holes too and they are rhode island reds. strangely they are only on one side of their beak.

 

[dalasgalas]

Could she have injured her beak somehow? I've had similar things happen to beaks and the beak just grew out the injury.