Specific gravity test could give you an indication. Put a cup of water on kitchen scales & rezero (tare), then hang your piece of mystery metal by a string into the cup of water - not touching the cup in anyway, note the weight.
Now minus that from the weight of your nugget. Then divide the original weight by this value.
Eg nugget 12g, water weigh 7g
12 - 7 = 5g
12 / 5 = 2.4g your specific gravity.
Pyrite can be hammered, but it tends to go crumbly & dull.
I think you might have a Nickel alloy, it can have a yellowish tinge & be found near gold deposits (as we have seen recently in Kimbadala).
Nickel is magnetic, gold responds differently - see video.