I'm not sure which wall you are dealing with, but common sense tells me (since you can see daylight) it is an interior wall without flooring or base trim. It is hard to get basement floors exactly level so if it is a short gap of a few inches, then construction adhesive or foam sealant would be OK and not a whole lot to worry about. If it is a gap longer than 6' or so, I would put down some shims (if load bearing) and then glue or seal it. Double check the floor and make sure there is not a large low area that could trap water. Post back. Good luck.