I have quite a pronounced lump on the lower right side of my abdoman which feels very firm compared to my left hand side. sometimes dull nagging pain ?

Lipoma: you may have a lipoma. Ask you doctor to check it or you at next your visit. are you on any anticoagulation like Plavix, (clopidogrel) warfarin or xarelto?

Abdominal mass: I am not sure of your age, but at least it would be good for you to be examined by a physician, maybe have an abdominal or pelvic ultrasound or both depending on exam, and if 50 or over or with a family history of colon cancer or its risks, a colonoscopy, etc. Start by making an appointment with your primary care physician on Monday unless your symptoms worsen, then ER. Stool? constipated?