What Causes Thin Grain Of Rice Like Structure In Right Side Of Palm?

It feels like there is something loose in my right side of the palm of my left hand, its been there for a while now. Only noticed it a couple of months ago. Feels like a bone chip or something, feels sorta long & thin like an overgrown grain of rice. I don't remember ever falling or hurting my hand at any point. I can only feel it when I squeeze it & it kind of hurts a bit when I do. But it doesn't really bother me. I just want to know what it is.