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The indentation in the arm between muscles is unexplainable from the injection of kenalog or depo both of which are steroid
hormones. i needs to be evaluated by a close look examination by a local physician.
in the middle of the night is related to faulty sleeping posture during deep sleep.
you may be having the arm under your body and it may compromise the blood supply and can compress the nerve
to cause numbness.
You should be careful not to lie down on sides, you can ask your partner to keep a watch on you whenever he/she is awake.
I hope the advise would be informative and useful for you.