How could a zippo do this to my chest?

Alright so my boyfriend has a zippo lighter and i always just put in in my bra to hold onto it. well the other day I did just that and then I started to feel an insane burn on my - for lack of a better word - boob. People thought I was being dramatic because you couldnt see anything. I took the lighter out of my bra. There was no lighter fluid - and the lighter had not been used recently (aka it wasnt hot) --- I felt as if I could feel the fluid going into my veins and what not. --- The next day I had a huge red spot where the lighter had been, in the shape of the lighter. It didnt hurt --- next day it started to bruise a little and now its peeling and it isnt swollen just a little tinny bit puffy --- Just enough that I can tell its there if I run my finger over it. What happened?