It is unfortunately not possible to change the house you have been allocated after sorting. Remember only the Sorting Hat knows which Hogwarts house you belong to – and it knows best!
Using the Wizarding World app, anyone who has previously been sorted on Pottermore will be able to re-take the Sorting Ceremony and discover their Hogwarts house. If you are sorted into a different house, you will be able to choose either your new house or to keep your existing one. You do not have to change your house if you do not want to.
You will not be able to take the reimagined Sorting Ceremony on WizardingWorld.com if you have already been sorted on Pottermore.