Hiya I just don't want to trouble my doctor so need advice

I have had this on my ankle for a number of years it has spreadup my leg and down my ankle, used to think it was a burst vein or something, but hubby says it's feels like my ankle bone has shrunk and its itchy, feels like the skin is breaking down around dark area. Used to love the sun when younger not so much now though. Had cancer in past non hodgkins 10 year remission. 

Thank you all x