As others have stated, take it out, put it in a fireproof container, and call Apple ASAP. Luckily lithium batteries will not explode with shrapnel involved, however they create a mean fire. I use LiPO batteries in my hobby, and we have to have a bucket of sand on site in case a LiPO is damaged or believed to be damaged, in which case the battery is thrown into the bucket. If there is time, one slices the battery open, and places it in a 5 gal. bucket of saltwater solution for 1-2 weeks for it to slowly discharge, in which case it is chemically stable and safe to toss in the trash.