I have a small scab on my back i'm afraid it may be skin cancer. ?

Need to examine: It is not feasible to provide an opinion without looking at the lesion. It may be seborrohic keratosis, an non-cancer lesion, but it would be prudent to see your doctor for an in-person evaluation.

Be proactive: hi I don't have any mention of your age so determining the probability of this been cancer is a bit harder the best thing to do is to have it examined. A good skin examination will reveal if you need to have any concerns. the best thing to do now is to have a physician look at your scab and the rest of your skin. best wishes and happy holidays