Erections during a dream are normal, but here we are talking about a dream of erection. Symbolically, this points either to fear of impotence or to the joy of masculine power. This symbol is about willpower and vitality within men and women. It almost always poses the question of how goal-oriented and focused your actions are.
For men as well as for women, this dream can be interpreted as the need for hetero-, auto-, or homosexuality.
According to Freud, women dreaming of erection indicates penis envy.
[1]The penis is the ultimate phallic symbol, an image that represents masculine power. An erection is the implication that that power is ready to be put to use. This is so no matter the gender of the dreamer.
If you have the erection in your dream, you are ready to take action in some area of your life.
If someone in your dream has an erection, then the aspect of your personality symbolized by that person is the one that currently needs to be called upon to provide the power you need.
[2]1. Power, energy.
2. Exercise control.
3. Desire for someone.
[3]