Out of context, it's very hard to know for certain. If found in or near moving water, whether tidal or 1-directional river, you'll find one side worn like that. I've found many that have fooled me for a second, but then I realize that there are too many just like it, and it just ain't possible. That would also explain the funny little hole, which could have been a bore hole (eroded) or an inclusion of another rock that popped out- another thing I've seen a lot of near/ in rivers and tidal areas.
If, however, it was found in the woods with other bits of debitage, flakes, etc, then yah, could be. Pretty lumpy and smallish- not a formed pestle, but perhaps a pestle of convenience- a rock found and used as was.
So, no context, no real answer, IMHO.