An i the asshole for calling off work?

Hi, i work for a fast food place (20 yrs old). I recently got a chemical burn on my ear and the back of it, too. The day after i went to work and left early for my appointment, which my boss did not like.

My doctor said it was a serious third degree burn and would get worse before it got better. He also wasn’t happy with me that i came to work instead of going right away. He prescribed me an ointment, but last night i was in so much pain that i couldnt sleep. I was up until 5 am and knew there was no way i could do my shift.

I called in three hours before it started and informed the same manager that the burn was serious and I’d make it to my next shift. He wasn’t happy at all and asked if i could grab some painkillers somewhere to try and stick it out. I told him that wasn’t possible right now. He told me straight up that i was putting him in a sucky situation and hung up.

Was i the asshole here? I would supply pictures but they’re graphic