HI.Lower abdominal pain
on left side needs to be evaluated for Colitis/Left Ureteric colic
. If the pain is associated with mucus in stools,it might be large intestinal infection.Cough
raises intra abdominal pressure,so you are getting pain .You should exclude Inguinal hernia
on left side also as the swelling increases on coughing ,but subsides after lying down.All the best.