As you know, shingles is a viral disease that involves the reactivation of the chicken pox virus Varicella, which lies dormant in the body for many years. It gets reactivated when the body's defenses are down for one reason or another. When shingles occurs, it almost always shows up on one side of the body. A few itchy sores on one arm does not sound like the typical description of shingles. The number of sores is not as important as their distribution and the symptoms that go along with them. Most people with shingles complain less about the itchiness and more about the pain, which can be severe. The rash is usually fairly distinct, and thus is not likely to be mistaken by a doctor
who has seen it before. If this was shingles, and you did not have a lot of skin spots or pain, then it must have been a very mild case.
I think it is worthy to note that it is a bit unusual for an otherwise healthy young person to get shingles. If you happen to develop a similar symptoms, and you are diagnosed with shingles again, then I think you should have an evaluation of your immune system.
In the mean time, it would be good for you to schedule an appointment with your primary care physician
. He or she can make sure that you are up to date with all of you immunizations including the Zostavax, the shot for chicken pox/shingles. This can at least partially protect you from it happening again.