The itching can be a sign of skin cancer. Moles don't usually itch. But don't panic. Many skin lesions that are cancerous are often the less serious types. Definitely get it checked out. I just had one removed from the back of my neck because it had changed. It was precancerous but the dic said it would have taken several years to grow into a malignancy.
http://www.melanomafoundation.org/prevention/abcd.htm