Ganglion cysts do not cause swollen lymph nodes unless the cyst is malignant (like synovial carcinoma). Also, a malignant cyst would cause swollen lymph nodes on the same side ---left foot: left groin. The best way to determine if the cyst is malignant is to perform a aspiration of the cyst and send it to pathology for analysis (which can be performed by your podiatrist). Lymph nodes in the groin usually should be a little bigger than a pea size. IF they are much bigger, consider having your physician perform a sentinel node biopsy and examine the foot leg for skin neoplasms (skin cancer). UTI's (urinary tract infections) or other GU problems could also cause enlarged nodes in the groin too.