It could be nothing to worry about - just fat tissue.
Most often, a lump in the abdomen is caused by a hernia. An abdominal hernia occurs when there is an area where the muscles are weak, and this allows the internal organs to bulge through the abdominal wall.
The further plan of management would involve -
'-Blood tests including full blood count, electrolytes, urea, creatinine, liver function tests, pregnancy test and lipase.
-Imaging including erect chest X-ray and plain films of the abdomen
-An electrocardiograph to rule out a heart attack which can occasionally present as abdominal pain
If diagnosis remains unclear after history, examination and basic investigations as above then more advanced investigations may reveal a diagnosis. These as such would include
-Computed Tomography of the abdomen/pelvis
-Abdominal or pelvic ultrasound
-Endoscopy and colonoscopy'
Let us know about what your doctor advises and if you need any further information.