Yes should be fine to water the edges as long as you don't disturb the middle where the root mass is and should already contain moisture since its been watered already. You could also water the pot tray if its in trays and let the growing medium soak up the water from the bottom as well.
If you've got any wooden toothpicks/cocktail sticks at home they come in handy to check moisture levels. Just dip a toothpick a couple of inches into your growing medium away from the centre and pull it out. Works like a dipper on a car and it should show you up to where the moisture level is or if there's any moisture at all. Also just let the toothpick dry by a window and you can reuse it.