Did you read the post about Nizoral at the top of the page? I'd start there; it's cheap and easy to try.
@oboogie is right though, we're not doctors. I've been lucky, but I've heard that a lot of doctors have a negative bias towards tattoos. That may be why there's the "too bad, you're stuck with it attitude." When the dermatologist didn't prescribe anything and told you it's a granuloma, did you ask any questions?
I'm not trying to be a dick, but stand up for yourself and take a little initiative. It took me literally two seconds to find this article - https://www.mayoclinic.org/diseases-conditions/granuloma-annulare/diagnosis-treatment/drc-20351323. That's where I'd start.
Sorry, but not sticking up for yourself is one of my pet peeves. I had a friend that was diagnosed with plantar fasciitis. His doctor told him to stop exercising and stay off it. I just about exploded. I told him to tell the doctor that that was unacceptable and what were his options. He wound up getting anti-inflammatories and physical therapy. It healed much faster and didn't reoccur, which would almost certainly have happened if he's just stopped using it until it was better and went right back to what he was doing before. YOU are responsible for your medical treatment, nobody else.