My daughter whos 3years old fell last night and landed on her arm ,she can move her arm but is complaining that its painful. is it broken ?

Maybe not, but: Depends on details. Increasing pain and inability to move the arm after a fall or accident means a trip to the ER or to the orthopedic doctor's office to be examined. If there is lots of swelling, numbness, or discoloration in the arm or hand, the situation is an emergency because the blood vessels and nerves may be damaged. For mild symptoms, an office visit to her pediatrician should suffice.