Ouch...I'm just trying to mentally visualize this happening, and I'm having trouble seeing how your arm is in a position to get pinched by it. Maybe just keep your arm away from that until the doors lock, or change your routine when you first get in to include locking your door before you start driving. It's been proven that a new habit can be formed in about two weeks for most people. So for two weeks keep a post-it in your truck to remind you to do that. It will quickly become as much of a habit as putting on your seat belt. Or just remove the nub, like already suggested.