I masturbate by moving tip of my penis in circular motion.there is no up- down movement and hence the foreskin hasn't opened up completely. is it ok?

Not really: How does a guy wash the head of his penis (the glans) each day in the shower, if he cannot pull the entire foreskin back away from the glans? Between ages 5 and 15 or so, the foreskin gradually loosens by itself (or with gentle help from its owner) so the boy can wash the end of his penis (just like any other body part) during daily showers. Tight foreskin can be helped by his primary care doctor.