how long does a butt-cheek stay flat after injury?

i was on the top ladder working on a Christmas tree decorating it with doggy and cat treats. i wasn't paying attention the to ceiling fan. the ceiling fan blade smacked me so hard that i flew off the ladder and slammed my butt-cheeks really hard through a big wooden table. the table snapped in half.

one of my butt-cheeks became literally flat and lumpy and feels strange to sit on. how long can a flat butt-cheek stay that way? is it permanent?

i hope i don't need a implant to repair it. help?