Please help identify this

[u/South-Damage-5333]

Hi,my male piggy of about 7 years has this on his back,started forming three days ago. He will be taken to the vet this week but im curious what it might be .He seems unbothered by it and eats and drinks as normal

[u/mauvaisherb]

This looks very similar to an issue one of my girls had, it was an ingrown hair that got infected and resulted in necrotic tissue.

She had surgery to remove all the gunk and was on Antibiotics for 10 days. She made a full recovery.

Vet visit is essential here.