Where on your head did you press that it dented in? The only place that should be soft is right in the center of the back of your neck, around where your hairline may start. That's where the spine ends.
I'm really happy they found nothing in your scans. Do you know what type of scans they did?
So "Acute non intractable headache, unspecified headache type" means it had an abrupt or sudden onset (acute), lasts up to 72 hours (non-intractable), and they don't know what type of headache it is (migraine, tension, etc.
I hope you get some relief soon.