I have had a hard lump in my groin for around 7 weeks with no other symptoms. the swelling has gone but the lump is still there - what could it be?

Lymph node: Could be a lymph node. This can be from an infection of some type, but also could be from a lymphoma. Lumps in the region of lymph nodes need to be looked at by a doctor, and if suspicious, will need to be biopsied to ensure is not worrisome.

Hard inguinal node: Hard node for seven weeks is a serious problem. It can only be confirmed by biopsy. Please see a general surgeon. Interestingly you have no symptoms like fever, rash, discharge , sexual history. Please don't delay because more than two weeks is enough time to be concerned. Thanks and good luck.