Hello,
Welcome to the ehealthforum and I am really glad to help you out. Pain in the forearm can arise from injury or inflammation that affects any of the tissues of the forearm, including the muscles, bones, blood vessels and tendons. It can be due to tendonitis or inflammation of the tendon at the elbow that radiates down through the arm.
I suggest you to apply cold compresses and take some anti inflammatory pain killers after prescription from your doctor. Give complete rest to the part and avoid doing any activity which causes any further damage.
I sincerely hope that helps. Take care.