What Are The Red Scaly Spots?

I have a small reddish spot (size of a match head) that is slightly scaly. No itch or pain. Seems to be getting larger very slowly. Had a full set of tests at a clinic for STDs and am clean. All I can think is eczema or psoriasis. Any ideas? Treatment? I am 57 years old, 5'8" tall, 155#. No particular medical problems...