When the neck is strained & a pop is heard & now there feels like a weird air bubble moves when touch n the back of head low crown also dizziness why?

Neck Bubble. You might have subcutaneous emphysema. Read===>http://en.Wikipedia.Org/wiki/subcutaneous_emphysema and see if it might apply to your history. Even so, if it is truly sir trapped in the neck tissues, you need to have a thorough evaluation and tests from your doctor to get to the root cause.