Hi. This weird plant started growing out of nowhere

Question

I got a tomato plant and this little seed was growing. I put it in its own plant and it’s growing fast. Any idea what it is? Thanks

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Answer 1

It could be horsenettle, which produces poisonous berries. I'm attaching more information:

https://njaes.rutgers.edu/weeds/weed.php?horsenettle

https://www.gardeningknowhow.com/plant-problems/weeds/get-rid-of-horsenettle-weeds.htm