Hard lump

[Farleigh1]

I have what feels like a very small (1mm) lump on my back. It is on the surface of the skin as if it has been stuck on. Its not coming from within the skin. It is very hard. I picked at it loads but it never came off. It almost seems like a acrochordon (skin tag) but everywhere states these skin tags (acrochordon) are soft!

What can this be?

Thank you