You have herpes simplex, the virus that causes gential herpes. In this case it may not be an STD, But it's possible, especially with a routine appearance. Testing may not be all that necessary unless it gets worse, but keeping under control is. You need to not have physical contact with your lips and anyone's mucous membranes on the time of infection (when you have a coldsore!) because you'll transmit the virus. You'll also always have the virus... So be ready for cold sores.
I've been getting cold sores since I was a small child. My father got them and two of his siblings did too. There is a medication that prevents cold sores from emerging if you take it as soon as you feel the tingle. I carry this medication with me and take it. The last time I got the tingle, the cold sore disappeared immediately. It's called Apo-Valacyclovir 500mg (valacyclovir). It's a one day dose of 4 tablets taken immediately and then four later in the day.