Any ideas what this could be?

[Oaktree79]

Hi there

Does anyone knows what this is? It looks like an abscess and it has become bigger over time. Thank you!

 

[Eggcessive]

That appears to be an ear infection or abscess. It can be bacterial, viral, fungal, or from mites. I would get some hydrogen peroxide, QTips, paper towel or tissue, and plain Triple Antibiotic Ointment to get to work on cleaning out the ear. Here is a good article and look for the post #4 by @dawg53 :
https://www.backyardchickens.com/threads/ear-infection.767500/

 

[dawg53]

It looks more like Ear Canker; here's a link:
https://www.chickenwhisperermagazine.com/health-and-wellness/ear-canker