Put it in ice. During the first 24 hours after overworking a muscle, apply an ice pack to the affected area. Apply the ice no more than once every hour for no more than 20 minutes at a time. Ice constricts blood vessels in the area and minimized fluid loss in the surrounding tissues that causes swelling and pain. After the first 24 hours the chance of swelling subsides and heat is the preferred treatment.
Heat increases blood flow to the area and promotes healing.
Of course, severe, disabling pain or tenderness that does not go away after a reasonable period of conservative self-treament should be seen by a physician. But following the simple methods used by athletes as mentioned above can help you get new muscles in shape and prevent injury.