Hi there,
I am Dr. Deepak, I work in Emergency Department, where I see many patients with
injury to their head. As you mentioned you had injured your head pretty hard by falling on a metal chair, and you don't remember hitting and how you went to bed.
I feel you had sustained minor injury to your head, I can say that as
1. you didn't had any dizzy feeling.
2. You didn't had
vomiting even though you had
nausea..
3. You are not feeling any
numbness or weakness of any one side of your body
4. You are not having any blueish discoloration around your eyes and behind the ear
5. You are not having any trouble with walking.
And after recovering for the effect of alcohol you are feeling pretty much fine.
You can wait and watch if any of the above mentioned problem appears, then you can visit a doctor and get yourself checked up. For the time being you can apply few ice packs over the dent and take some painkiller for the pain.
Thank you
Hope your concern was dealt with and hope you have a speedy recovery.