my 5 year old son has pain in his right arm, no bruising nor signs of being hit, pulled, falls, etc. the pain is not severe, but bothers him. He does not have as firm a grip in his right hand as in his left. He feels sore in all areas of his arm (forearm, elbow and upper arm).
Hand grip getting weak is something you have to take care whether it's just an injury or neurological weakness. May be a brachial plexus pull injury or wrist or fingers injury? The description of pain is not clear about the site. Give a course of painkiller (paracetamol 150 mg) for 2 days and if still complains with weak grip get him examined by or tho.