Why does my csection scar still hurt?

Painful scars. If your scar is recent, it may take sometime to stop hurting because the healing process takes awhile. While the scar may seem solid, collagen remodelling occurs as well as nerves growing back in and this can make a scar sensitive. It could hurt if there is a hernia or infection so if the scar seems to be hurting more each day or there is swelling, pain or fever, see your doctor!
How long has it been. Post-surgical scars can be tender for many years. Usually worsening with changes in the weather. If your surgery was recent (past week or two), or if there is redness or swelling around the wound, you should have the surgeon who operated you check it out.