If you're leaving it alone (not poking at it or picking at it) and it appears to be growing, I'd say that warrants a check-in with your doctor. However, melanoma doesn't usually itch. It could be another type of skin cancer: https://www.webmd.com/melanoma-skin-cancer/news/20140723/painful-itchy-patches-could-be-sign-of-skin-cancer
Your height, weight and age aren't really relevant here, but your skin type may be. If you are relatively fair-skinned, your chances are higher of developing skin cancer. In any case, a lesion that doesn't go away, and increases in size, merits at least a visit to your GP.