In a deep wound, there might be a few layers of tissue that need to be rebuilt because they were lost. In this rebuilding process this pebbly texture can be seen and it indicates that granulation is taking place (that's the process). Granulation is when small blood vessels and capillaries start to develop vertically to the outside part of the wound, being supported by connective tissue, and surrounded by cells of many other types for different purposes, such as immunitary functions or specialised tissue functions. This tissue growing is characteristic of healing and it presents this granulated/pebbly texture to it.