It's strange to think that there could be a time where you didn't know what you looked like. This isn't really up to the standard of most answers on askhistorians (I'm usually the one asking the questions!), however I mostly wanted to reply to suggest that the average person could probably see their reflection in water in ponds and what not.

Apart from that, I know we have had mirrors throughout most of human history, made of bronze and copper, so some people definitely would have access to a clear reflection of themselves. However I'm unsure if the typical medieval commoner would have had access to them. Which leads to a follow up question of my own: assuming easy access to reflections were not available, would it have been common for towns to have publically available mirrors or reflecting ponds specifically for this purpose?