I have a pain in my left forearm, my diagnosis is : GROWING PAINS.
"Growing pains are a normal occurrence in about 25% to 40% of children. They generally strike during two periods: in early childhood, among 3- to 5-year-olds, and later on, in 8- to 12-year-olds. No firm evidence exists to show that the growth of bones causes pain. The most likely causes are the aches and discomforts resulting from the jumping, climbing, and running that active children do during the day.
Growing pains always concentrate in the muscles, rather than the joints. Most children report pains in the front of their thighs, in the calves, or behind the knees. Whereas joints affected by more serious diseases are swollen, red, tender, or warm, the joints of children experiencing growing pains appear normal. Although growing pains often strike in late afternoon or early evening before bed, there are occasions when pain can wake a slumbering child. The intensity of the pain varies from child to child, and most kids don't experience the pains every day. Although growing pains often point to no serious illness, they can be upsetting to a child - or a parent. Because a child seems completely cured of the aches in the morning, parents sometimes suspect that the child faked the pains. However, this usually is not the case. Support and reassurance that growing pains will pass as children grow up can help them relax."