How do I tell if this is a mole, and if it's cancerous?

I'm a 15 year old male, and I have a pinkish, reddish bump on the backside of my thigh, I think it may be a mole, I noticed it about a year to 2 years ago, I think it may be cancerous, what are some symptoms, and how can I tell if it is indeed cancerous? I'm scared, so...