My 3 yr old son complains of legs pain oftenly, what could be the cause of it

A. there are multiple causes of limb pain during this age because it can be normal due to growthx pain. it can also occur due to nutritional deficiency mainly vitamin b12 iron and calcium deficiency. if there is excessive playful activity by the child during the daytimex it is but obvious that during the night time there might be limb pain. if the limbs are paining without any activity then yes medical examination and treatment will be required