Blister and now brown spot after eMatrix/ two. (Photo)

I got ematrix treatment done 2 weeks ago. After ematrix dr used a device to stimulate collagen. So basically an two treatment. She went a little higher setting than what they use for first time patients but not the highest. Second day of treatment, I had a small blister on left side of my cheek. It's now turned into brown spot. Did she burn me? I'm not sure what it is as I understand that those treatment can't burn you. I have a follow up soon but I can't stop thinking abt what could that be.