Deep scratch in outer rubber door frame, drivers side.

Just noticed a very strange deep vertical scuff / scratch on my drivers door rubber surround seal on my Monte Estate.

Anyone else ever had a scuff or scratch appear in the hard rubber that surrounds the top outer part of the window, between the glass and car? I can't possibly imagine how it's got there and it's really ugly. Looks like it's been cut in by a car key or something similar.

Is it even possible to get stones fly up that could freakishly cause a deep scratch in the rubber? Literally I have no idea how I'll repair this one without a new rubber surround.