Thank you for your question. Molars can sometimes become rotated during braces treatment and it rarely is a cause of concern.
Towards the middle or prior to end of treatment your orthodontist will be able to straighten it again before removing your braces. Do remember to keep it clean as rotated molars do trap more food than normal. This is only temporary until the molar is straightened up again.
Please do talk to your orthodontist about your concerns as communication is key to successful treatment. I hope this helps and good luck!