If you need to get the neck straighter Nick and the truss rod nut feels tight, don't force it. If you are confident in doing the work yourself, you need to get the neck straightened by clamping it. This will take the stain off of the truss rod. Then try loosening the nut first, just to release it. You should then hopefully be able to tighten it (after apply a little lubricant), sometimes an extra washer needs to be added but not always. All being well, this would do the trick.
If you need a bit more detail, happy to chat via pm or phone.