I'm assuming this aileron is covered in some sort of iron on covering:

Typically, you would apply a little more than enough twisting force on your aileron straighten (ie, over corrected) and apply the heat from an iron while holding the twisting force. Let the aileron cool before releasing the twisting force and it should relax to a straight condition.

If it's already on the plane, you might try disconnecting any drive linkages, or pushrods, lock the root of the alieron in the neutral position by clamping it and the fixed portion of your TE between some scap ply, then applying the twisting force to the tip of the aileron, while heating both sides of the aileron.

hope this helps
-Elliot