I'm sure there are better or more refined ways to do this, but this has worked for me. Heat up your clothes iron to a pretty high heat, about 3/4 on mine. I always take an old washcloth and wet it, wringing out some of the water. It works better if it's just soaked, but not dripping wet. The moisture in the cloth is where you get your steam, and it dries out as you use it. I double it if it's a thin cloth, and place it over the ding. Place your iron over the cloth, using as small amount of the iron's surface as necessary. I use only the tip on most small dings. Keep trying this until you get the wood to expand, keeping a wet section of the cloth in use at all times. I've never had a problem with the wood getting burned. This works on most dings, and even a few gouges.
*I wouldn't have suggested this on a finished stock with any coating. You shouldn't have any problem on a sanded one.
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Blessed are the peacemakers: for they shall be called the children of God. Matthew 5:9