My son received a vaccination when he was about 1 1/2 the nurse had mentioned to me that some parents think the shot leaves a mark that resembles a freckle on the skin. She assured me that it doesn't, but sure enough there it was. It grows as he grows and everything. Why did the vaccination give him a freckle?

I would advise having the doctor take a close look at it but it most likely is a scare from the puncture.