I can think of a few different possibilities here, but narrowing them down and arriving at a diagnosis will probably require that you go see your primary care doctor
. If the spot is not improving, then you should definitely be seen.
One possibility is that this was an insect bite of some sort (a bed bug, mosquito, spider, etc). Bug bites often provoke an inflammatory reaction that can give a red, slightly raised look to the skin. Often they are quite itchy and you may notice a small mark in the center consistent with a bite. Generally bites don't require any treatment unless they get infected (painful, warm, very red) or if the skin in the center looks like it is breaking down.
Another possibility would be a contact reaction of the skin to some new skin care product, just like you mention. Although this would usually be more diffuse, it could be localized. Although you say you haven't used any new products, you should also think about potentially new laundry detergents or fabrics!
is a condition in which scaly, dry patches of skin can develop. Mild eczema often responds to moisturizing, although sometimes medicines are necessary.
Start by talking to your primary care doctor.