I am 20 and I go to a great university and I work full-time.

Health wise, I was going to the gym regularly and even started to lose some weight (I am 5'5" and range between 165-170 lbs) I carry my weight well, but that is beside the point.

I DO eat a lot of salt, but I eat pretty healthy. I went to the doctors recently because I had a month long cold. They took my blood pressure and it was 140/90. The nurse didn't even really mention that is was that high and the doctor didn't seem to care. When I mentioned it to my mom I went to the doctor's and told her my blood pressure she flipped out (she used to me a nurse) because I guess it is usually pretty low.

I figured I can improve my diet (less salt) and start working out again (ugh). I am going to go back when I find time in my schedule.

Anyhoo, should I be concerned at all? Family history generally has low BP (I think... )

Right now you have no cause for concern. You could have been experiencing "white coat fever" which is very common when visiting a doctor. To have a diagnosis of high blood pressure, your pressure has to be high for 3 consecutive visits. One visit is not enough to diagnose HTN.

As you said, it would be best to lower your salt intake as well as caffeine.

It is unusual for young people like you to get high blood pressure. A blood pressure of 140/90 is considered borderline. There are many other factors that can lead to a transient high BP such as not enough sleep, taking steroid, and taking your BP soon after some light activities. 'white coat hypertension' is a phenomenon where you have a transient high blood pressure due to your nervous reaction on seeing a doctor. I suggest that you repeat your blood pressure checking. Before that, make sure you get plenty of sleep and rest for 30 minutes before checking your BP. If your BP remains high, you should get some blood investigations to rule out other diseases leading to high BP.