Can't set my mojang username as my new migrated java edition username

Hey guys,

I just tediously migrated my account and when I try to launch the game (minecraft: Java edition) it prompts me to enter my username, I then wrote my old username, and it didn't work, so I checked namemc, and apparently it is still attributed to my now deleted mojang account, please help me, I really liked this username and all my old friend on minecraft know me by it.