I Have Had A "barnacle" On My Arm For Several

I have had a "barnacle" on my arm for several years. In the last six months, it has started itching, the color is inconsistent, the border is more jagged and it is no longer flat but is now bumpy. I had Basil cell carcinoma on my face approx. 5 years ago. My Mom had a history of Squamish cell carcinoma. I am Blonde, Green eyes and age 49. Everything I've read says that I should see a doctor immediately however, I can't get into the Dermatologist until the second week of January. Should I try to see my primary care physician right away or wait until January to see the Dermatologist?