Yeh it sure looks like a pimple, I wonder if the other leg has one, if so Well we know the answer to that mystery.. LOL As he get's a little older he'll get the 2 or 3 very long feathers on the top. I tried to zoom but it didn't give me the option. Perhaps that would explain the cockiness.LOL...
all chicks have spur bumps and even some hens develop spurs (have 2 outside with spurs)

