A shatter cone ?

Indeed a strange formation

Interesting piece!  It's great that the piece has one side sawn flat to show a fresh cross-section of its interior.  Good photos, too.

Pillow lava is an interesting suggestion, but I doubt it for two reasons:  the exterior surface consists of convex polygonal segments that I don't think would form on pillow lava (or if they did, there would be clear cracks around them), and I doubt that pillow lava would form with a sharp layer boundary as we see here.

I'm inclined toward botryoidal growth of something like goethite.  It looks fairly solid and pure (not many cavities, and not a mixture of various different minerals, at least at a macro scale), so a specific gravity test (https://www.mindat.org/a/determining_the_specific_gravity_of_a_mineral) would help narrow down possibilities if you have the means to do it.  Try a streak test:  scratch an inconspicuous corner on an unglazed white porcelain surface such as the base of a coffee mug and observe the color of streak it leaves.