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.
I agree with yakker that the context of the relic being found is important. Where is was found, what state? By water? Is it a field find? Creek or what exactly?
In my view it is a rock with a common shape somewhat like a pestle, not a pestle.
I have found only two small pestles. The rock is less than 2 inches in length from the last photo. The smallest I have found was 3 inches. It was very well made with a nice grinding area, tapering to a nice rounded top which fit the hand nicely.
Most range from 4 to 7 inches in height for bell or hoof pestles. A bell pestle is the easiest pestle form for me to identify in the field when scanning the ground due to the unique shape. Roller pestles come in many sizes in my area, the largest I found was 8 to 10 inches in length.
That item would not be classified as a bell pestle.
Virtually all hoof pestles I have found have a conical form tapering to a rounded top. None have the shape as that item.
I found two bell pestles this summer, both in corn fields. Here is one, note the shape, the dimple is visible on the bottom of the pestle.