This sounds like the eczema I have in the same place. I would ask your GP not a dermatologist, this sort of thing is really common. If you can get a topical steroid cream like triamcinnilone (spelling error) and apply it (ask your pharmacist for a recommendation for a good topical steroid for eczema if triamcinnilone isn't available OTC) apply it twice a day for a few days. If the problem goes away its probably eczema or psoriasis. If it is it will probably come back after a week or so of clearing up with the steroid. This would serve to alleviate your immediate fears of cancer, but you should still mention it to your doctor, who can suggest some dietary changes that might be really simple and also prevent it from coming back. I just use topical creams for my flare ups.
Hope this helps.
I would go to a dermatologist and see. Peace of mind is worth everything.