I am not sure exactly what this is, and I suggest that you get it checked out by your primary care doctor
in order to reassure yourself. I can think of a few possibilities but you will need to have it directly examined by your doctor in order to be sure.
One possibility is a fungal infection of the skin. Fungal infections (tinea corpus) often show up as spreading, ring-like areas, often with a bumpy, tough texture to them. They may be reddened with a lighter center or they may itch. They are quite easy to treat, and they often only require topical anti fungal creams.
Second, another potential would be eczema
, which is a condition in which the skin becomes dried out, reddened, itchy, and flaky. The condition responds to treatment with topical steroid creams and good moisturizing and skin care.
I would worry
too much that this is a tumor at this point. Your primary care doctor, of course, will be able to perform a good physical examination and will be able to rule this out for you. Furthermore, they will be able to diagnose what exactly the condition is and what you should do next to help get rid of it!