**Core Concept**
The question is testing the management of a common skin condition in children, specifically a bosselated erythematous lesion on the cheek, which is suggestive of a molluscum contagiosum infection. Molluscum contagiosum is a viral skin infection caused by the molluscum contagiosum virus (MCV), leading to the formation of characteristic skin lesions.

**Why the Correct Answer is Right**
The treatment of choice for molluscum contagiosum in children is topical imiquimod cream. Imiquimod works by stimulating the body's immune system to fight the virus, leading to the destruction of infected skin cells and resolution of lesions. It is a topical treatment that is easy to apply and has a good safety profile, making it an ideal choice for children. The mechanism of action involves the activation of toll-like receptors on dendritic cells, which then stimulate the production of cytokines and interferons that help to eliminate the virus.

**Why Each Wrong Option is Incorrect**
* **Option A:** Isotretinoin is a systemic retinoid used to treat severe acne, not molluscum contagiosum. It is not indicated for this condition and can have serious side effects.
* **Option B:** Metronidazole is an antibiotic used to treat bacterial infections, not viral infections like molluscum contagiosum. It would not be effective against the MCV virus.
* **Option C:** Corticosteroids are used to treat inflammatory conditions, but they can also suppress the immune system and make viral infections worse. They are not the treatment of choice for molluscum contagiosum.

**Clinical Pearl / High-Yield Fact**
Molluscum contagiosum is a common skin condition in children that can be easily treated with topical imiquimod cream. It is essential to diagnose the condition accurately to avoid unnecessary treatments and to ensure the best possible outcome.

**Correct Answer:** D. Imiquimod cream.