Welcome to the STD forum.
Eczema is a dermatologist's bread and butter. Misdiagnosing eczema would be like me not recognizing gonorrhea. Since a dermatologist believes your rash was due to eczema, that is also my belief.
Oral sex is safe sex. There are STD risks, but they are low; and if you caught an STD by oral sex, the only possible manifestations would be penile sores, blisters, or discharge -- or maybe painful urination. Nothing else. Most likely the "scaly spots" on your penis are simply due to eczema involving that part of the body. Your description doesn't even hint at genital warts, and you cannot catch warts from oral sex; and warts cannot appear less than 4-6 weeks after exposure.
If you remain concerned, return to the dermatologist. Or feel free to get a second opinion from your nearest public health STD clinic. But in the meantime, relax. Nothing you mention suggests any STD.
Good luck-- HHH, MD
Thanks for the help on this. My only concern is that the raised skin appeared farther up on the base of the shaft rather than the area where my penis and skin folds meet which is where the original eczema was diagnosed. Also,the raised skin is different in appearance from the other areas of eczema. I may be overeacting. I will see if it gets better over the next few days.
The appearence of eczema and many other rashes can vary quite a bit from one body part to the next. If you remain concerned, return to the dermatologist for conformation that you don't have two different skin conditions. But whatever you have, the description does not suggest any STD. This has nothing at all to do with the sexual encounter you describe.
Feel free to report back the dermatologist's second opinion, or the result of a visit to another provider. Until then I'll have no further comments.