Common furniture beetle exit holes are generally 2 - 3 mm in diameter. Those look about the right size, so that's a possibility.
As Sideways says, seeing exit holes indicating adults have left doesn't mean there aren't more grubs from later egg laying activity burrowing away inside. Slainte.
Being that small I can't hazard a decent guess. Powder post beetle grub exit holes are usually about 1.5 mm diameter, so even that's a rather unlikely candidate. Sorry I can't help. Slainte.