Attempted to talk to someone but wimped out

I'm 23M with not great social skills and anxieties so already socialising is hard, I had a good day out with a close friend and we talked over a lot of stuff and honestly I was feeling good about myself at the time I saw a woman in a really nice outfit on the train home and thought it would be nice to compliment it. But before I could say it I wimped out and just got off at my stop. Seems I still need to work on my confidence a lot if just a simple "cool outfit have a good evening" made me wimp out.