It is most likely a lipoma. These are benign tumors made up of normal fat cells, just a large collection of them. They have no color or skin changes with them. They feel soft, or like other areas of subQ fat.
They are usually left alone. If they are in an area that cause functional problems or the cosmetic appearance is not desirable, then they can be resected. But, you essentially trade a lump for a scar.
If, however, the lump grows in size very rapidly or becomes painful, then it should be evaluated.