How can you tell the diffrence between a pimple and Basal cell carsanoma?

I have these three spots on my arms. I thought they were just pimples but they haven%26#039;t gone away. I will probaly get them checked out but I want to know if I am totally over reacting. I live in Florida so I am outside all the time.|||Yes yes yes go get them checked asap. Could also be dermatofibroma (benign) those can sometimes look like an ingrown pimple. Best to have a reputable dermatologist look at it and do either a shave or punch biopsy-done in office while awake with local anesthetic-piece of cake. CALL for APPT TODAY!!!!!!!!!!!!!!!!!!!!!|||Pimples taste more salty than carsanoma.