2003 Nissan Sentra AAA battery inside Gas Tank

Electrical problem
2003 Nissan Sentra 4 cyl Four Wheel Drive Automatic

Dear Sir,
My Grandson put a " AAA battery" inside
the Gas Tank. Does it cuuse any dangerous situation
while a start the engine? Is it OK to start the engine?
How can I take the battery out? Please tell me what
to do.
Thank You
George Boyd