Parotid gland swelling or parotitis: This condition could cause a hard bump near the TMJ due to inflammation of the parotid gland, which is located close to the temporomandibular joint. The sudden onset could be due to a viral or bacterial infection.

Abscess or cyst formation: An abscess or cyst in the vicinity of the TMJ could present as a hard bump, especially if it has become infected or inflamed.
Lymphadenopathy: Enlarged lymph nodes in the area could feel like a hard bump, potentially due to an infection or inflammatory process.
TMJ disorders: Certain conditions affecting the TMJ, such as a dislocated disc or osteoarthritis, could lead to swelling or a palpable bump in the area.

Parotid gland tumor: Although less common, a tumor of the parotid gland could present as a hard, painless bump near the TMJ. Early detection is crucial for effective treatment.
Metastatic disease: In rare cases, a bump near the TMJ could be a metastasis from a distant primary cancer. This would be particularly concerning in patients with a known history of cancer.
Salivary gland stone (sialolithiasis): A stone in the parotid gland or its duct could cause sudden swelling and pain, potentially feeling like a hard bump near the TMJ.

Benign tumors (e.g., lipoma, neurofibroma): These could present as a hard, usually painless bump near the TMJ but are less common.
Infectious diseases (e.g., actinomycosis, tuberculosis): These could cause swelling or a mass in the area of the TMJ, although they are rare and often associated with systemic symptoms.
Autoimmune disorders (e.g., Sjögren's syndrome): These conditions could lead to swelling of the parotid glands, which might be perceived as a hard bump near the TMJ, but they typically have other systemic manifestations.