**Core Concept**
The patient's symptoms are likely due to the accidental infiltration of a local anesthetic into a nearby nerve, causing numbness in the lower lip, chin, and tongue. This is a common complication of dental procedures involving local anesthesia, particularly when the inferior alveolar nerve is inadvertently injected.

**Why the Correct Answer is Right**
The inferior alveolar nerve is responsible for sensation in the lower lip, chin, and tongue. When local anesthesia is infiltrated into this nerve, it can cause numbness in these areas. The inferior alveolar nerve is a branch of the mandibular division of the trigeminal nerve (CN V3). The symptoms described are consistent with an inferior alveolar nerve block or infiltration, which can occur when the anesthetic is injected too close to the nerve.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the symptoms described. The mental nerve is a branch of the mandibular division of the trigeminal nerve (CN V3), but it is responsible for sensation in the lower lip and chin, not the tongue.
* **Option B:** The lingual nerve is a branch of the mandibular division of the trigeminal nerve (CN V3) that is responsible for sensation in the anterior two-thirds of the tongue. While it is possible for the lingual nerve to be affected by local anesthesia, the symptoms described are not consistent with a lingual nerve block or infiltration.
* **Option C:** The buccal nerve is a branch of the mandibular division of the trigeminal nerve (CN V3) that is responsible for sensation in the cheek. It is not responsible for sensation in the lower lip, chin, or tongue.

**Clinical Pearl / High-Yield Fact**
To avoid this complication, dentists should use a "dry" technique for local anesthesia, where the anesthetic is injected without any bleeding, and should also use a nerve stimulator to confirm the location of the nerve before injecting the anesthetic.

**Correct Answer: D.**