I was a stupid teenage and thought it'd be cool to burn 5 dots down my upper arm with a cigarette

I very much regret it because now it's very noticeable and embarrassing

it's been a few years and I never treated them, they first blistered and than healed and now are completely flat but the color is darker than my naturally olive skin tone,

what can I do to get rid of them as quickly as possible?

I have olive skin and experienced similar scaring from flaming hot oil when I was a chef. I had blistering on my hands but my chest and arms got the worst of it and eventually had the dark marks like you're describing. It took some time, maybe 4-5 years, but they totally disappeared. There may be some new stuff out by now, like Mederma that may help, but they should vanish with time. Good luck.