What do you think is the best thing to do about my front teeth? (photo)

I had braces before and before it was removed,all my teeth are perfectly align. But after a yeat i think, my front teeth are starting to move until it became like this(photo). They never switch me to put a retainer but when I return that my teeth is already like this, they recommend to put me a retainer. But its too late. Pls help.

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