john deere diesel leak

Hi everyone, I own a 6200 and noticed a leak recently. The diesel comes out when it's running and comes out on the left hand side of the engine..to the left of the filter and to the left of the diesel pipe. It looks like a bleed screw and when tightened holds a wire with a metal tip under it. I have tried tightening it but I'm worried I will.Ness up.the thread or damage the wire. Any tips or advice??

Thanks

john deere diesel leak