Tip: Copy the PIN into the app. With some phones, you just need to tap the grey box to have the code from the SMS automatically entered - or you can see it on a banner that appears at the top for a few seconds. Finally, there are phones where you must go to your messaging app to see the SMS and back again in the MitID app to enter the code.
The MitID app you have on the phone you used to scan your passport is still active. If you no longer want to use it, you can delete it or keep it as a backup for your new MitID app, so you always have access to MitID.