Ingrown pubic hair is one of those things you never want to see together in a sentence, but it's also common, even if no one talks about it. This video by Stuff Mum Never Told You explains how it happens, and what to do about it. Basically, whenever you regularly shave, tweeze or wax, the hairs can grow back into your skin (because you've shaved against the grain or have a layer of dead skin that keeps the hair from growing outward) and become ingrown hairs. In some cases, these can become painful or inflamed. Ingrown hairs are much more common in places that have curly or coarse hair, like around your crotch.
The obvious solution is to just stop grooming down there, but that would be too simple, wouldn't it? If you're really invested in pubic hair removal and want to minimise the chances of those dastardly ingrown hairs, the video suggests trimming your hair first, soaking in a warm shower or bath, using shaving cream and not soap, shaving with the grain and exfoliating to clean up those dead skin cells. But for some people, it may not be possible to completely avoid ingrown hairs.
Ingrown hair down there [Stuff Mum Never Told You]