I spent a little time tonight thinking about anatomy and artistic conventions, namely, mine, on both counts:
Most animals with horns don’t have necks as flexible as a dragon’s, so the risk of self-stabbing is considerably less.
However, I think that I’ve figured my personal dragon out so that he won’t, but I’m probably wrong.
(Mostly I’m thinking about last night’s sketch- I basically broke both the horns in order to make them fit, instead of placing them higher or the neck lower.)