Hi welcome to Health care magic forum.
Thanks for calling H.C.M.Forum.
your husband is diabetic, hypertensive, and he is using medicines, for them. Now he is having pain in the left lower abdomen , it constant and nagging, since 4 days.
The pain in lower left side of abdomen suggest, urinary tract infection
, stones in the urinary tract
, or infection of descending colon
, or rectum
. Previous medical history have no relation with the pain.
I advise you to consult a surgeon for diagnosis and treatment. You may need to have an M.R.I. besides other routine tests for confirmation.
Wishing for a quick and complete recovery.