Hey Spam,
Noticed you are in the cold State of Rhode Island. Get your foam wall into an area at least warmer than your tank water/lighting will be for curing. If not, then the foam may experience a "post-cure" resulting in more expansion and the release of more isocyanates into your tank.
Personally, I would give it at least a couple weeks cure time at 80 plus degrees to be safe as there will be trapped gasses in the pores of the foam which you want to leach out.