Bartholin gland cyst: This is the most common diagnosis for a yellow nodule in the vaginal wall, particularly if it's located near the vaginal opening. The Bartholin glands are located on each side of the vaginal opening and can become blocked, leading to cyst formation. The yellow color could be due to the presence of pus or thick secretions.

Lipoma: A benign tumor composed of fat tissue, which can occur in the vaginal wall and may appear as a yellowish nodule due to the fatty content.
Vaginal leiomyoma (fibroid): Although less common than uterine fibroids, vaginal fibroids can occur and may present as a firm, yellowish nodule if they outgrow their blood supply and undergo degeneration.
Sebaceous cyst: These are benign cysts that can form in the vaginal wall, especially in areas with sebaceous glands, and may appear yellow due to the sebum content.

Malignant tumor (e.g., squamous cell carcinoma, adenocarcinoma): Although less likely, any new or changing vaginal mass should be evaluated for malignancy, as early detection is crucial for treatment and prognosis.
Infectious abscess: An abscess in the vaginal wall, which could be due to bacterial, fungal, or parasitic infections, and may appear as a painful, yellowish nodule. Prompt diagnosis and treatment are necessary to prevent complications.

Vaginal endometriosis: Endometrial tissue can rarely implant in the vaginal wall, leading to nodules that may appear yellowish, especially during menstruation.
Dermoid cyst: A type of benign cyst that can contain various tissues, including fat, and may appear in the vaginal wall as a yellow nodule.
Vaginal xanthoma: A rare, benign growth consisting of lipid-laden histiocytes, which could present as a yellow nodule in the vaginal wall.