This sounds exactly what it was like for me the day after surgery. Painkillers may have been given intravenously with your fluids and after that is stopped basically the pain kicks in. It is because you have had operative work on your body and it is reacting to being cut, I suspect. The pain went in a day or two. The other pain I have found bad is indigestion but that starts going soon as well. If the pain gets worse, make sure you let the medics know. It is to be expected at first but should lessen rather than worsen. Keep smiling, you took the brave step and it is a great new journey of your life and health from here on in