No, don't just run to the gardai at the tip of a hat. If there's anything the world needs less of it's people who complain idly.
What sort of stalking is it? In all fairness, if it's phone-stuff you're probably best to just try to deal with it unless it's really sinister. He will get tired and give up, at least that's what happens me lol. (but like for if I'm sending some girl on youtube messages or something not stalking).