may burn off EVENTUALLY but in the mean time, if thats on the braking surface, thats a no no. id definitely clean/lightly sand those pads to make sure youre not stopping using a plastic coated brake pad.
Yeah if you are really worried, like mentioned, just pull wheel and caliper off and take bag off an then you'll be a-ok. Few hard stops and anything in there will be burned off and the pad will have a fresh clean surface to bite the rotor with. I wouldn't worry about it really, odd how it got in there though??? very unlikely situation but ehh nothing surprise me anymore haha