A couple of spots were missed getting sanded before the first coat of paint went on. Now I can see the spot. Can I lightly sand the spot and apply the second coat of paint?
Yes, but the paint will be difficult to sand. It will be rubbery. Try using 150 grit sandpaper and see how it goes. An alternative it ti skim over the area with a patching compound, spackling paste or whatever you want to use, and sand that back to a smooth surface. This might work but it depends on your situation.