Is it too late

Is it too late for my kid to wear sunscreen. She will be 3 already and has always gone out without it everyday last summer would go swimming n wouldn’t wear it.. I was dumb and wasn’t aware of how important it is but now I am. Can she still start wearing it or is it too late. She got dark and stayed like that and her skin on her arms got white bumps I’m pretty sure of the sun. This was since last summer she’s stayed like this. Also should she wear it every time we go out? Even if it’s not sunny or only when it’s sunny?