Hi,
To begin with, I have to emphasize that I am not a doctor of any kind, and am not licensed to do any official dream analysis. However, personally, from what you've said, I would guess your dreams are connected to that "trapped" feeling you've been coping with and a (very natural) desire to be relieved of that feeling. Since you felt better after hurting yourself in your dream, it seems like you associate self-harm with relief, even though you've never hurt yourself.
It's good to recognize this early—it gives you a chance to change that narrative without falling into hurting yourself for real. I would definitely suggest trying some things now, rather than later, to find some healthy ways to cope with your negative feelings that will help you feel better. One thing I've done in the past when I felt trapped in a situation was to sit down and write out every single possible solution, even the ones that seemed farfetched, as long as they were even a little possible. Just seeing that list helped a lot more than I expected. And sometimes the creativity involved helped me see options I didn't recognize before, and sometimes these were the options I chose in the end.
Journaling in general can be helpful too, as well as any kind of creative outlet you might enjoy. Self-care, too—taking good care of your body can improve your mental state more than you might expect. It can also help alleviate sleep disturbances, including nightmares.
If you're struggling with your dreams, or if you start to feel like you're struggling with self-harm urges—or honestly, if you're just struggling in general—consider asking for help. Commenting here is a great first step, but is there someone you can reach out to and talk with? A therapist or counselor might be a good idea, but if not, see if you can think of a close friend or family member who could help you through this. It's not selfish or weak to ask for help; if anything, it's brave. And it can help so much, both now and in the long run.
I hope that helps. If you have further questions, comments, concerns, etc. feel free to reply here or elsewhere on the blog. I'll reply as soon as I'm able.
Sincerely,
Kim
PS: I appreciate the Stranger Things reference in your name. :)