Looking for advice on treating burst abscess near hen's breastbone

[Eggcessive]

Yes, it is common to use it in chickens. Here is a thread about it:
https://www.backyardchickens.com/threads/how-do-i-administer-a-penicillin-shot-to-a-chicken.352701/

https://sites.google.com/a/poultryp...oultry-podiatry#chickens_penicillin_injection

 

[dawg53]

Her breast might be rubbing the roost when she perches for the night. Go out later at night with a flashlight and observe how she's sleeping on the roost.
Dont use Pramoxine HCI, it is not for use on blisters. Use betadine and neosporin to initially treat as Eggcessive mentioned. If it doesnt heal or gets worse; get her started on cephalexin or SMZ/TMP.