mmfs

I have a white lump with a black dot, it's about 3cm it's little but if I squeeze it together it feels as if I have a ball. It started really small with no pain or discomfort, I went to Dr. she said it would go away, it's been almost a year & it's grown a little bit still no pain but now it's uncomfortable esp. when I wear my seatbelt. Am just afraid it's cancer or something