First of all, it sounds like you haven't had a medical evaluation for your psoriasis yet at this point. Therefore, I would strongly recommend that you go to see your primary care doctor
or a dermatologist
as soon as possible. There are several different skin rashes
that may be confused with psoriasis, and so it is important to have a formal medial evaluation and diagnosis before proceeding to treatment.
Psoriasis, as you may know, is a form of skin rash that is caused by an auto immune reaction in the skin. The symptoms include a reddened rash that usually has a silvery white scale on it and that can be extremely itching. People with skin psoriasis also sometimes have deformed nails and joint pain or swelling.
If your doctor diagnoses you with skin psoriasis then, fortunately, there are several excellent forms of treatment available to you. If you just have a single patch on the hand, then your doctor will probably want to begin with a good topical steroid cream and see how that works. More extensive cases of skin psoriasis, or cases of psoriasis that include joint problems, often require oral medications rather than just topical medications.
Get in to see your doctor as soon as possible!