If it's not too bad sometimes twisting it the opposite way can fix it. I do it while strung and leave it that way for a while. If you draw it and let it down easy it'll lay in the groove when it's good.
I had a stubborn one recently that needed a hot water treatment. I strung it and twisted the limb past center while holding it under hot water til it's warm. Then turn the water to cold while still over twisting it til it cools. Leave it strung a bit then draw and let down. Repeat as needed til it stays straight.