It is probably a lymph node (inguinal) as it occurs in a lymph node region. Inguinal nodes are usually considered abnormal when larger than 1.5 cm.
Common causes of enlargement include infections in the area drained by this lymph node like the leg or foot, genitourinary or the lower part of the abdominal wall. Following recovery from infection or inflammation nodes regress in size but never to their normal size thus remain palpable.
Clinical examination is essential to define the characters of this swelling and the need for further evaluation by investigations. So, I advise you to follow up with your doctor.
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This answer does not substitute for direct medical consultation.
Dr. Safaa Mahmoud.
MB BCh, MSc Internal Medicine. MD Medical Oncology.
PhD Experimental Medicine and Biochemical Science.