I dreamt that I woke up from a dream, only to be stabbed my a masked man, then woke up gasping

In more detail:
I dreamt a dream in a dream (I don't recall what the inner dream was), and woke up into my first dream. In there, I had just woken up, the light from the outside seeping through the curtains was whitish-gray, and I didn't get up. My eyes fully opened, but before I knew it, a random man wearing a black mask like bank robbers do, came out of nowhere from behind me, grabbed my chest with his left hand, then stabbed me in the chest with a knife. When I woke from this dream, I got up extremely quickly, and without thinking of anything, my hand grabbed my chest where I was stabbed. I immediatly looked at where the assassin came from (which, weirdly, was my closet). The only thoughts that came to my mind where;
-What just happened?
-Was that just a dream?
-My heart's beating too fast.
-It's 5 in the morning!?!?!?
-This would happen a on a school say...

I just want to know if this is common and if it has any meaning about anything in my life.

It's a false awakening, but this is the first time I've ever heard of it being a nightmare...I would have pissed myself :p But False Awakenings are common so don't worry about it too much. I personally doubt it has any kind of deep revelation with your life though, just your brain trying to process something you've probably seen somewhere or something.

reality is a strange place, kids say all the time daddy or mommy! theres a monster in my closet! or cubboard.....
i done some strange research, and discovered that there are sort of portals in them closets, a sort of gate way for, *things* to use to access this world, but there *world* which is i believe is the false awakeing worlds that one can experience, that world floats very close to this world i believe but we can only access it, when we are in the correct state, but they too can access us......... you dont have to believe this, this is just my personal belief, i do not buy into the whole false awakening/sleep paralysis thing anyway thats just a cope out! in my book! they paint it scary thus giving people the idea that it cant be explored... i hate that term! for such a interesting state of mind to be in!!!!
i would perfer something like altered state of reality or something like that! because i personally know that realm/realms can be explored

What I learned from reality if that there is way more to things than what we see.

this is the one thing i feared when i heared about false awakenings.. Waking up to find a murderer in your room , wud probally scare me half to death

Thats what I hate in my false awakenings, they allways turn into nightmares (allthought the nightmare usually start when I leave my room).