What Causes Bump On The Penis Shaft?

i had this little bump on the upper left side of the shaft of my penis and i was sort of nervous and really embarassed by it. so i had began to pick at it and squeeze it cause it resembled a pimple. When i squeezed it a clear liquid came out but the pimple or whatever it was stayed there so i kept pushing the liquid out and now there is no bump, but now where the bump was at, the skin became darker, only in the area of the bump. is this a sign of something or is it just a simple scar?