Nice one Al
While my experince with groundwater has taught me there are no garantees, it is unlikely that adding the rocks would reduce the water level, infact I would expect the opposite given the added mass and the possibility that the porosity of the aquifer has been reduced, albeit very locally.
Chances are that the rise and fall are more likely to be linked to regional water level changes due to recharge event a while ago (possibly some snow melt from a few weeks ago
?) Are there any other groundwater users nearby, as their usage patterns could be echoed in your water levels?
Was there any rain between when you put the rocks in and tonight when you noticed the water level rise? This may have directly filled the voids in the rocks you have put in, but this hasn't percolated into the aquifer (yet) due to a much lower transmissivity and lower storativity in the aquifer.
Any photos of the site?
Does the water level in the pipe / bore match the water level in the rock fill?
PM me if you want any advice