Final answer:
The sharp pain experienced during needle insertion is likely due to the needle contacting the nerve sheath, resulting in nociceptor activation and pain signal transmission to the central nervous system.
Step-by-step explanation:
The patient experienced a sharp pain when the needle was being inserted, which is most likely related to the needle contacting the nerve sheath. When a needle breaks the skin, as explained in different figures, it applies a concentrated force which, unlike being poked by a finger, has the potential to cause significant pain and trauma.
Moreover, the pain experienced during dental procedures, like drilling, is known to be a result of cellular trauma where chemical messengers are released and picked up by nociceptors. These nociceptors then transmit signals of trauma to the central nervous system. Hence, contacting the nerve sheath with a needle can elicit a sharp pain through the activation of these pathways.