Hi Jen -
It looks like a slightly weedy member of the Aster family (aka composite family, aka Sunflower family, includes
dandelions). Members of this family can easily be identified by their classic "composite flower" morphology.
If you look closely, the flower has 2 types of flowers: flowers with petals (along the edge, called ray flowers), and flowers without petals (in the center, called disc flower). Then there is a row of phyllaries subtending the petals (green scaly things).
Sorry I don't know what it is! Plants in this family are most often used for their bitter agents. I'm guessing this plant is stinky and somewhat bitter if you tasted it.
Go ahead, taste! You can't kill yourself if you try a very small amount and spit it out.