I had one when I was 22. It was close to the breast and I had it removed. They told me that if it moves it's not malign (but, I guess they were just telling me that to stress me less ). I had it removed surgically (it was a piece of cake) and sent for a biopsy. After I got the results, they told me it was a good choice to have it removed.

I suggest you go to the doctor.

Sometimes, though, it could be only a limphatic node (not sure of the name in English) swollen from some infection on your hand or arm. Go see a doctor!