[At this point he's used to people asking about his scars, when he actually wears clothing that displays them. He is not used to people just straight-up touching them with no preamble, but he supposes he has to get used to casual touch now. At the very least he saw that coming, because if he hadn't he'd probably have punched her in the mouth on reflex.]

Those? Those are from bullets. Small projectiles fired at a high velocity, fast enough to pierce the skin and do incredible amounts of damage internally. Something like an arrow with hundreds of times the power behind it and no shaft to aid removal.