At just a few days post op after a tummy tuck, it is not unusual to have some pain and burning especially after coughing. It is also not unusual to have some swelling in the first week or two after the surgery. The swelling you are having is probably due to some fluid accumulation and doesn't necessarily mean that you damaged the muscle repair. If your doctor gave you a compression garment, be sure to wear it. Let your surgeon know about your concerns but don't worry in most cases this will resolve over the next few weeks. Best wishes.