Scared
My advice? Call your doctor on Monday. Now, my doc told me that unless my incisions were really red and hot around the edges what I was feeling was just the normal healing process - I felt a burning sensation, itchiness, and pain if I twisted the wrong way.
Is the "intense burning" from the incision or just a general pain in your left side? If it's not the incision, you might want to consider going to the ER today.