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I would say that you are not the only one who has ever had this happen. I have seen other posts from people on this site who have experienced something similar to what you have. Since self harm is a part of your life, in my opinion it is only natural that you would dream about it.

That being said, I'd keep your self harm tools out of your room or at least somewhere hard to get at for now, because if the dream gets triggering enough, you want to be able to avoid any urges you may have to self harm when you wake up.

It may also help to practice some sort of relaxation technique such as meditation or yoga before bed, or even just take a warm bath. Certain scents are also relaxing. At least this way you won't be going to bed as stressed out.