Legally...I've no idea.
Personally, there is no way that I would fly it, with fuel being fed from that tank. I've no idea how big the gap is for fuel to feed the engine, and hence no idea if
a) it's possible for the chain to block the gap, or
b) worse still, for the chain to pass into the pipe, and get stuck further into the system, and in effect cut off fuel from either tank.
I suspect you need to speak to your engineer before flying again.
All just my opinion....
dp