Been there, done that. Walked around for three or four years with a visible spot just up and to the left of where I was looking.....A tiny bit of stone embedded in my left eyeball. A big ol' blood vessel grew across to it and it finally dissolved.
On a somewhat different note, my brother whacked a bearing to split it off a shaft on our combine, and a bit of steel went in his forearm. Months later, he got a nasty infected lump, 'way up his arm from the entry hole. That thing went at least four inches through skin and muscle! Good thing it wasn't going straight in toward something he needs!