You have sap wood on one side and heart wood on the other. Most woods around here dry and shrink more in the sap wood than the heart. Looks like yours did the opposite.
You can use a heat gun and watch it very carefully to keep from blistering the finish or checking the wood or a steam heat will be much safer. You can always refinish if you bung it up. It's fairly easy to make a steam box, ask if you need some direction.
Get it hot all through and bend it back straight or a little past straight. Keep it straight well past cooling and it should stay. Some people would go to the trouble to build a form to clamp the stick in place while it cools. I think for just one piece with no more bend than that you can work it out by hand. You can reheat it and bend more if it needs it.