Battery swelling, my back glass is now being pushed off

battery is definitely bad. I’m unsure personally of what iFixit’s return/warranty policy is, so you’d want to check with them for sure.

that said, don’t try to “deflate” the battery or anything. it will catch fire at best and explode at worst.

Edit: also when you go to remove it, try not to use any heat on the device. swelling batteries are quite dangerous, and even heating the screen too much can cause problems. use ispropyl alcohol to weaken the adhesive and try to remove with a suction cup or such. if you must try to heat it remove the motherboard first and keep a fire extinguisher handy. just for a worst case scenario.