Gears, Welcome to NT.

Your delayed symptoms are delayed longer than concussion symptoms usually are. The doctor's diagnosis is meaningless. They do not have any tests for concussion other than the subjective complaints of the patient unless the concussion is severe and causes objective symptoms in a neurological exam.

I agree with Jo*mar. You likely jammed your upper neck and have upper neck inflammation. Such an injury will not show up on imaging.

Gentle therapy by an upper cervical specialist would be worthwhile. Gentle traction and range limited movement/manipulation is helpful for many.
DO NOT DO RANGE OF MOTION EXERCISES. They will likely trigger more inflammation. Icing your upper neck and being disciplined to maintain good head and neck posture when resting or sleeping is very important.

Your symptoms suggest upper cervical inflammation that impacts blood flow to the brain stem where heart rate and body sensations are processed.