Is a strong pounding heart and headache a sign of high blood pressure? Or even just a pounding heart by itself a sign of high blood pressure?
Can your blood pressure be high during these episodes and then return to normal?

Pounding heart is not a measure of blood pressure, but merely a consequence of increased cardiac force. In most instances, cardiac force is actually the result of preceding hypotensive spikes. There are baroreceptors, or pressure sensors, located in the ascending carotid arteries which provide feedback to the brain's cardiac center regarding blood pressure necessary to maintain adequate cerebral perfusion, without which you would experience syncope. In instances where blood pressure momentarily falls too low, the most expedient method for correcting the issue is for cardiac force to be increased, which you experiencing as forceful pounding beats. This effect is limited, however, since factors relevant to vascular constriction and dilation play a more typical and constant role in dynamics associated with blood pressure.

Pounding heart is quite common in persons with anxiety because of mild variability in vagal tone and other autonomic processes which can infrequently produce sometimes dramatic effects. A common example where such a response is most typically is one wherein a person is suddenly startled or frightened, a premise wherein vagal tone typically descends rapidly and in some cases causes some people to experience syncope or fainting. In lesser instances, this rapid and transient down-regulation of vagal tone is countered by a subsequent increase in cardiac force, which is why most people in the aftermath of a sudden frightening event will experience pounding heart. The phenomenon is usually described something to the effect "My heart feels like it's leaping out of my chest!"

With the exception of extremely few instances, blood pressure cannot be felt or sensed, hence its common descriptor as the silent killer.

You'll be fine. There is nothing of such an instance to suggest anything is wrong other than the influence of anxiety upon physiology.

Best regards and Good Health