Why Do Healing Wounds Feel Warmer To The Touch?
This is a normal part of the inflammatory process. Inflammation is your body's localised defensive response to tissue injury of any kind, and it is characterised by four cardinal signs- redness, swelling, heat and pain (severe inflammation involves a fifth, loss of function). 

Your body is performing three main processes here:


Mobilisation of the body's defences.

Involves release of vasoactive chemicals, which cause the blood vessels to dilate and increase blood flow to the area. This causes the pain and heat, The blood vessels also produce cell-adhesion molecules which make immune cells (leukocytes) stick to the walls of the your blood vessels.
Containment and destruction of pathogens.

The immune system then goes to work clearing up any bacteria which have got into the wound. The leukocytes release chemicals called cytokines to attract more immune cells, to contain and destroy bacteria.
Tissue cleanup and repair.

Dead cells, cell fluid and other debris (pus) is then absorbed by the lymphatic system. Platelets and endothelial cells then secrete growth factors which stimulate cells called fibroblasts to multiply and produce collagen. The heat also increases metabolic rate and increases the rate of tissue repair.