I'm sure this is a weed, I've got a few of them cropping up. Dont want to remove them and then find out it was something I had actually planted (it does happen... )
It looks like a seedling of a campanula variety. I'd leave it be for a while and see what happens.
Arh funny you should say campanula, I think I remember throwing some seeds out the back as I have them in the front. Must have worked after all.
Glad I asked. Thank you. haha, I've taken up plants so often. Should learn unless it is ground elder, leave alone until I've asked on here.