there is no widely known or documented information about Prince Harry being nicknamed "Bunker Harry" during his time in the military. Prince Harry served in the British Army, and he undertook two tours of duty in Afghanistan.
During his military service, Prince Harry was known as "Captain Wales" to his fellow soldiers, in reference to his official title, Prince Henry of Wales. Like other soldiers, he likely had various nicknames among his comrades, but there is no specific evidence or widely reported information regarding a nickname like "Bunker Harry."
It's worth noting that information might have emerged or changed , so I recommend checking more recent sources for any updates on this topic.