Infection (such as pneumonia): The rapid appearance of the nodule over 7 days suggests an infectious process, which is more likely than a malignant process given the short timeframe. The spiculated nature could be due to surrounding inflammation.

Lung cancer: Although less likely given the rapid onset, lung cancer cannot be ruled out, especially in a smoker. The spiculated nature of the nodule raises concern for malignancy.
Inflammatory nodule (e.g., due to an inflammatory reaction or a granuloma): This could be a reaction to an infection or another inflammatory process, and the spiculated appearance could be due to the surrounding inflammation.

Pulmonary embolism with infarction: Although less common, a pulmonary embolism can cause a rapidly appearing nodule, especially if there is infarction of lung tissue. This diagnosis is critical to consider due to its high mortality rate if untreated.
Tuberculosis (TB): TB can cause nodules that appear rapidly, and it's essential to consider this diagnosis, especially if the patient has been exposed to TB or has risk factors for TB.

Wegener's granulomatosis (now known as Granulomatosis with Polyangiitis): This is a rare autoimmune disorder that can cause lung nodules, but it would be unusual for it to present as a single, rapidly appearing nodule.
Lymphoma: Although rare, lymphoma can cause lung nodules, and it's essential to consider this diagnosis, especially if the patient has systemic symptoms or other risk factors for lymphoma.
Metastasis: If the patient has a known primary cancer, metastasis to the lung is possible, although the rapid appearance and spiculated nature would be less typical for a metastatic lesion.