Matzot (plural of matza) have no inherent sanctity. As such, you can treat these boxes as you would treat two new boxes of cookies that were left in the waiting room. You can give them away, open them and eat them, discard them, etc.
Judaism doesn't like wasting valuable things (it is called Bal Tashchit, see here and here) but two boxes of matzot are not that highly valuable and fewer people will want to eat them after Passover.
Nevertheless, it would be great if you found a productive use for them. Maybe leave them in the waiting room with a sign that whoever wants them is welcome to take them home?