It's usually a common thing that happens, shouldn't be much of a cause to worry!
I have thalassemia minor so I'm really susceptible to dizzy spells, especially in the first trimester - what I learned to do is to bring an "emergency kit" everywhere I go: umbrella, plain water, sweets/fruit juices (something for quick energy), wet tissues, light snacks etc.
Also made sure I told everyone where I'm going and try to avoid the crowds whenever possible, if I could, I avoided going out or at least going alone too!