I've been riding on country roads where the road shoulder is gravel. Some cars and trucks see a few cyclists and head for the opposite shoulder to give us more than enough room. They can flick up lots of little pebbles and I've been sprayed once or twice.

It's not nice but nothing serious.

On the other hand, a friend of mine had the same thing happen on a ride we were on. A small pebble hit him in the shin and caused a nasty sore. He continued riding for a couple of days but it got nastier. He ended up spending a few days in hospital.