I have kept safety pins tucked away in my EDC bags and range gear for years now. They are small, weigh almost nothing, and can be stowed in really out of the way places. They also happen to be useful for a myriad of tasks like impromptu clothing and gear repairs. The only thing that I ever used them for that was even remotely like a medical procedure was picking splinters.
Tac Med Solutions, makers of some of my favorite medical kit items like the OLAES Modular Bandage and the SOF-T Tourniquet, has a video on Youtube that shows just how versatile a safety pin can be as an addition to your first aid kits. This is improvised gutter medicine at its finest.
After you watch the video, you absolutely should subscribe to their Youtube channel. It is tremendously informational and they have videos that detail the use of many of their products. These videos can be an invaluable training aid (though not a replacement for actual in person training).