I don't see you'd need to seek permission (from whoever) if it's obviously fallen over recently. Digging it out of the ground, reerecting it and putting gravel round it might be a bit much. But if you can obviously see where it went, surely there's no harm? When the Blind Fiddler fell over I guess that needed a bit more effort to put back and to secure safely so it didn't fall on top of the next visitor.