Is this a weed or a good flower. It came on its own.
A weed is simply a plant growing out of place, where it is not wanted. So, you could have an orchid growing in the middle of a field of wheat, and the orchid would be the weed. I don't know what plant you have, but it looks pretty. If you like it there, then it's not a weed. If you don't want it there, then it is.
That looks to me like wild geranium - I think it's also called cranesbill, but could be way wrong on that. I love these! I purchased mine to get them started, but there is a lavender version as well that grows wild in the woods everywhere here.
looks like Anemone canadensis
It is an Anemone.