With a BP like that, you are not really gonna stroke out on the spot or anything (during intense exercising your BP spikes to some insane numbers, so you're probably safe from any immediate risks), but the problem with hypertension (or as Bandaidwoman pointed out, prehypertension which increases risks of hypertension later in life) is that it increases your risks for tons of health problems later in life, namely heart failure and coronary artery disease. Over time it can beat up the kidneys and cause a slew of other complications.
Lifestyle modifications can and should be implemented now. DASH diet is a good place to start (just google it, tons of info). Obviously monitoring it is a good thing too, once a week or bi weekly unless you really want to be detailed and do it everyday to see how events in your life, diet, training may impact the readings. I also don't completely trust those stupid ones they sell that measure your BP themselves. Better to get a cheap sphygmomanometer/stethoscope and learn to check it yourself, its not hard and more accurate IMO.
Also, an inadequate stress outlet will lead to physiological changes (htn being one of them). So if you have a stressful life, tend to worry, be anxious etc, look into stuff like meditation, take warm baths, maybe some aromatherapy, or simple things like listening to calming music for 30min/day, or taking walks to just clear your mind and such can help.
As to the question about whether your reading warrants medication, its a tough call. Maybe bandaidwoman (hopefully she'll be around to help out) can shed some light, she'd know a lot better than I. A call to the doc wouldn't hurt, I mean the criteria to diagnose HTN is two readings with a minimum of 12 hours apart, i believe.
Take home message is, you can start to implement changes in your lifestyle now which can possibly control your BP on their own, monitoring your BP regularly is never bad and a phone call or a MD appointment can't really hurt.
