Hard lump under skin, pubic region

I have a really hard lump under my skin. It’s technically on my butt cheek but very much in the inner where I shave. It has absolutely no head and hasn’t ever had one. It doesn’t show signs of having pus inside. You honestly wouldn’t know it was (it’s skin color) unless you touched my butt cheek. I can almost feel it roll under my skin when I pinch it. Any idea what this could be? I’ve had it close to a month so I don’t believe it’s an ingrown hair. Also sometimes it can hurt when I sit if it get irritated, when irritated it enlarges.