There is surgery for nodules, but you need to go to a real expert. Sometimes the results are worse than before. I think a famous movie star (Julie Andrews?) had the surgery, and then said that she was unable to sing afterwards. They use one foot long very narrow instruments to reach inside and try to clip off the nodules, something like scissors, but sometimes they can shake and they may accidentally clip off part of the vocal cords. It is not simple.
I knew a baal tefila who was told they cannot rule out cancer unless he had the surgery. Thankfully the nodules were regular benign things, and his voice was still good, afterwards, but not as strong as it was before.
I guess if the voice is so bad it really sounds like gravel, you have nothing to lose, but if you are just looking for a minor improvement, it would be risky.