I am also 5 days post-cataract IOL surgery, and my pupil has been small and is also still very small, but now appears to be enlarging somewhat.
On my day after surgery visit, the Dr. said they had applied a medicine during surgery to keep the pupil small. So, this is expected. During this visit, my eye was temporarily dilated by drops and opened up normally, then went very small again after a few hours so I'm not aware of any reason for concern.
As usual with anything to do with my eyes and vision, it's extremely hard to be a "patient" patient, but I'm trying my best. Best wishes for your recovery.
I had a crystalens implanted and a miostat solution was instilled to restrict the pupil to a smaller size until the lens was healed in place. This effect was about 5 to 7 days as I recall.
It's a little unusual to have the pupil smaller since the pupil is widely dilated for surgery. It's still early and the normal inflammation after surgery could be irritating the iris making the pupil small. Ask your surgeon.