This volunteered itself in my garden. I wasn't sure if it was a weed and now I'm glad I didn't pull it up because yesterday these purplish blue flowers emerged. It has spiny leaves...It's about 2 feet tall.

I'm thinking it might be nigella, but wanted to ask the forum.

Here it is squeezed between my cosmos, 4'oclocks and bachelor's buttons:

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Here's a closeup of the leaves:

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