Hello and look up the facts before you see the dermatologist. Most people that get skin cancers are over 50 and the only skin cancer that is really dangerous are internal skin cancers called melanoma. Most people get a pink sore that doesn't go away called Basal Cell and it can be removed very easily and is not a life threat. Blood tests don't show skin skin cancer an only a biopsy can tell and they are only done if the doctor thinks it looks suspicious. Dermatologists know by looking at your skin and can tell you what kind they think they are. I have had 4 Basal Cells skin cancers all found at age 58 and I play tennis and am in the sun a lot. You can google skin cancer pictures to look at some pictures but you could have 100s of moles and not ever have one skin cancer. Even if you do the Dermatologist can burn off or cut out w/o a problem. It can get kind of expensive though. Take care and stay out of sun between 10 AM and 4 PM.
I hope that helps and don't worry about it because worry doesn't solve anything.