It will be fine to carry on using it in your tank and it will help to prevent it being passed to your other fish. I would suggest a partual water change to as some times bad water condition can cause odd infections in fish. Once the spots have gone just keep an eye on your fish as further treatment may be nessary. Red streaks in the fishes fins and tail will also indicant if the water condition is not correct. Its more likely that this white spot was laying dormant and has now come out with a bit of stress also with the fish being moved about.