welcome to healthcare magic forum
thank you for your query
what you have are sign of your age only
there is no direct relation between masturbation
and acne .
acne is due to hormonal
change in body .
do not pick or scratch it .otherwise it will leave marks .
you can apply clindamycin
base medicine .
masturbation is very natural and do not harm body so do not feel guilty .
if lesion persist better to consult dermatologist
i hope i answered your question