I can see why you would find a dream like this disturbing. I love dogs and I would find the dream disturbing as well. If you feel there is an issue on if the dream was from the Lord or not, then I would pray and ask the Lord to either repeat the dream if it was from Him or to show you the same dream in a different way.
If the dream was from Him, then I think it might be telling you symbolically to think of a dog as faithful friend, and in this dream you are basically dissecting this dog that is already injured. Did you take apart anybody with words lately? Sometimes hurting people don't want to be analyzed, they just need to be listened to.
If you feel the dream was just a stray one and not from the Lord, then I agree just file it away.
in Christ,