Chosen Solution
So after a month of using this iPhone 6s. It started to smell like a pierced battery. But on the top. It starts to smell when i press on the display harder. Any solutions? Thank you.
I would say either open the phone to check the battery or take it to the shop to get the battery checked since the phone is older the battery could have been damaged causing the smell.
Fit a new battery. Piece of cake to do and inexpensive.