The blossom is supposed to lose its effect if sent to camp, or brought above ground/into bright light in any way.
Getting sussur bloom stuck on your character permanently when you do not have a sussur bloom anywhere near you is very clearly an unintended situation, so, yes, that is very much a bug.
If you can spare the time and energy, I'd recommend submitting this one to their official bug report form (here:
https://larian.com/support/baldur-s-gate-3#modal), with some replication instructions a save file ready to reproduce it (make sure to include the whole folder for the save, including the thumbnail).