slowto280
Cover your back!
Report definitely....common sense....to protect you and your operator. It's all about liability. If you pass on the information to the relevant authority and they do nothing about it....you've done all you can in the short term. Imagine that the FOD caused damage or affected another aircraft in some way....perhaps being thrown up and puncturing a fuel tank.
Sometimes a regulation isn't needed, sometimes it is just the right thing to do.