It's on my left bicep
"Ouch" yes this is a shingles rash I am sure
Please go to your GP asap to the medication you will need.
Yes Eric! I had it on my arm too. Ideally you should see a Doc within 72 hours of rash appearing but I went even though it was a bit longer due to Easter hols. I was given anti virals but still got a couple more rashes and the pain! Fingers crossed you get there in time. 
That is Shingles, with a capital S! Read posts by me recently. Good luck and don't scratch!
Do go to see your GP, you need to have the right treatment within the first 72 hours. This can stop complications such as PHN. This is worse than the shingles and can last a very long time. There is also lots of advice out there to help you. Good Luck.