I never stumble upon this kind of issues when looking for healing / infected tattoos, neither allergic reactions. My artist thinks that's a reaction to maybe the soap or patch adhesive, and a doctor thinks it might be something about the ink used. This appeared on the second day, and on the third (today) worsened, which prompted me to go to a doctor. They gave me an antibiotic cream with corticosteroids.
I wanted to share this because I'm obviously wondering what could have gone wrong - ink allergy? Needle contamination or allergy? Folliculitis? So far this is very itchy. Hoping it will heal properly.