Thank you for your replies.
Woody and Johnny, the mortar is still sound so you've put my mind at rest. I'll wire brush off the marks and maybe keep an eye on that cracked brick over winter. The bricks on the front garden wall are spalling quite badly, but that's another topic.
Hi All,
This morning a 7.5 ton truck belonging to a delivery company hit the side wall of my house. It left a sizable skid mark and created a fine crack in one of the bricks. The wall is sound otherwise.
Is this anything to worry about? I'm slightly worried that the crack will expand with time...