What I’d recommend: humidify it for several days. Oil the bore lightly with almond oil. If it has keys, cut little squares of plastic wrap and slip between the keys and body till the oil is absorbed. Play for 5 minutes once or twice a day. If it absorbs the oil quickly, oil again after a few days. Gradually increase playing, and for the first few months oil it when it looks dry, up to once a week.
For many years I played a boxwood flute by Rudall & Rose at their 1827-1837 address and every piece was totally straight.
It was a typical 8-key flute, sterling blockmounted keys, and ivory cap and rings. Lovely both in appearance and tone.