Sycamore shoots?
Just pull them out.
Let it grow for a week or two, if it's Knotweed, it'll shoot up quickly for identification. Difficult to say if it is at this stage. If it is, get advice on professional clearance - it's illegal to spread it and you could be in bother!. Can grow from tiny sliver the size of your fingernail.Japanese knotweed! Oh boy are you in trouble......