Cause of solid enlarging lymph nodes in groin area (crease of upper legs), hard like stones, non-tender, many on both sides, enlarging for a month now?

See a doctor: lymph nodes are not to mess with. you need to see your doctor for proper evaluation and treatment. it could be granuloma. or a lipoma, or hard cyst. either way see your doctor.

Lymphadenopathy: Lymph nodal enlargement could be from reactive enlargement form infection/inflammation in the near by structures or infection/inflammation in itself, growth in the lymph gland like in lymphoma or spread of cancer from other sites, have it examined by a physician and may even need a biopsy for the diagnosis.