It's perfectly normal. I'll be *ugh*40 in two years and I'm already stressed about it! :)
20 is kind of a weird birthday. You're no longer a teenager and you still can't go into a bar and get a drink. It's like the limbo year of your life.
There's nothing wrong with having one tattoo.....I had only one for many years. Currently, I have three, and will be getting one more in the near future.
The definitive comment comes from that eminent Bostonian surgeon, Major Charles Emerson Winchester III. He said, "Tattoos are the common man's way of sponsoring art."