The only way to really know the diagnoses is correct you need to make a appointment with your doctor and go in and get some testing done so they can give you a proper diagnoses. Or you can do an internet search and it will pull a bunch of different things you can check out.
You are probably bitten by an insect or have got some infection of skin. If itching is more than pain, then you have allergy to something you used recently.
The pain can be due to the cartilages gap, that of the spinal Cord's problem. The Best advise to approach the best Orthopadic Doctor, and start treatment, this includes the excercises.