What Causes Breast Pain, White Bumps And Crust On Nipple?

I am 19 years old and had my first child a little over 10 months ago. About an hour ago my left breast started to hurt and when I looked at them I notice white-pimple like bumps on the aerola of both of my nipples. Also, there is crust directly on my nipples. There is no chance that I may be pregnant again. Should I be concerned?? What could be the cause of this??? Thanks.