As the others say get that off ASAP!
Corrosion has already started on the simm socket, see attached.
You need to neutralise this with Distilled Vinegar/Lemon Juice & scrub off with Tooth Brush and then clean the area with Isoproply Alcohol.
Make sure you let it dry properly before testing and keep fingers crossed there is no further damage under that simm socket like tracks.
Also, can't see behind the battery but are the chips legs covered in green too?
All the best.
Steve.
