I had a C-section about two weeks ago o just after the cesarian o notice a smal hard ball just were my cesarian ends in the inside what it could be?

Inflammation. Most of the time if there is no redness or drainage, a small hard lump may be inflammation or scarring from the fascial closure. This is usually felt more easily on the edges where the sutures are knotted. Ask your doc if the area becomes larger, red, hot, or painful.
Multiple things. Lumps underneath incisions can be attributable to a number of things. The fascia (strength layer) of the abdomen is closed with stitches that are tied together, so the lump could be the knot. A seroma is a sterile fluid collection that can collect. An abscess is an infected fluid collection. Sometimes a bit of blood collects, called a hematoma. Rarely, intestine pops out which is a hernia.