Usually the internal temperature is higher than the skin temperature as the temperature on the surface of the skin is reduced by heat getting dissipated to the external atmosphere.
The internal body temperature for warm blooded organisms has to remain constant for bodily chemical reactions to go on at a normal rate. If the internal temperature rises, the body reacts by starting the production of sweat and increasing the blood flow to the capillaries in the skin which help in releasing the extra heat. When internal temperature falls, we shiver; the muscles in our skin contract; and blood supply to the skin is reduced to prevent loss of heat.
The skin acts as a barrier to our losing internal heat or being affected by very hot temperatures externally and is the primary organ responsible for thermo-regulation.