Can Fordyce spots turn into pimples (or what look like pimples)? Can they become irritated, by masterbation?

Here are some... The likelihood for Fordyce spots to get infected like pimples is extremely low since they are ectopic - not hair-follicle-related sebaceous glands. Over physical stimulation by masturbation may potentially induce unwanted irritation to certain area of foreskin or penis, which you would be the only one to know by experience. More or in doubt? Seek evaluation & counseling.