What you probably have is a tendinosis (lack of blood supply to the tendon causing damage) or tendinitis (imflammation of the tendon) from prolonged overuse and spasm of the extensor muscles of the forearm. Both are commonly called tennis elbow. Prolonged muscle spasm and tension / pressure on the tendon can cause a wringing out of the blood supply within the tendon leanding to damage, or microscopic tearing of the common tendon of the muscles that allow you to power grip and extend the hand and fingers. Easily treated if that is the case.
Since it is most frequently a cumulative trauma condition, meaning microscopic damage that slowly develops over time, the treatment starts with first identifying and modifying the activities that cause the stress in the first place. ALot of the damage may be coming from repetitive hand movements at home and on the job that involve repetitive bending of the wrist ( as with hand tools, keyboards, etc) or repetitive power gripping (handtools, steering wheels, handles, or in the case of scooting, the power gripping the brake or throttle handles inappropriately)
Here are some things to look out for. Keep a loose but controlling grip on the throttle and do not keep the fingers constantly on the brake (or clutch) pull as this is stressful when maintained for long times. Use your cruise control when you can.
Keep the wrist from excessively bending when using the throttle or when using tools or your hands on the job.
If on a long ride, stretch the forearms when you take a break or at a traffic light. Pumping the fist open and closed repetitively 20 times also stimulates blood flow into the forearm muscles.
the use of a Cho Pat strap across the forearm can take pressure off of the tendon to give some temporary relief. (you can google cho pat)
You can treat the inflammation and muscle spasm of the back of the forearm by starting with cold compresses (ice) at the outside of the elbow where the tendons attach to the bone. this where your pain probably is. Apply for 15 minutes at a time several times a day. Motrin or other antiinflammatory meds will help too. After a day or two of ice you can begin to stretch and strip the muscles of the outer forearm. Using a hand cream, soapy water or other lubricant, you can strip the muscles by pressing in on the muscles with the thumb of the other hand just below the elbow and strip down toward the hand with pressure in the direction of the bones about 1/3 to half way down the forearm. Do not press directly on the boney area that hurts or the tendon itself within an inch of that boney prominence. You want to press on the meaty areas only as this is the muscle. Also do not press within 4 inches of the wrist as this is where the tendons and nerves are vulnerable to injury. Strip the muscle down about 20 times. It will hurt. You do not want to get black and blue after however.
After stripping the muscle you can stretch it by making a closed fist and with the other hand bend the wrist gently as far down as you can go without pain. Normal range of motion is about a 90 degree bend at the wrist without pain or pulling sensation in the muscle. If you have pain in the wrist, or significant pulling in the muscle itself, you have some damage there.
Finish with a heat pack for 10 - 15 minutes or so to increase blood flow into the muscle. If you find increased discomfort after the heat, use ice instead.
Do this once or twice each day and this will speed up your recovery significantly as well stimulate muscle regeneration. Strengthening exercises for the wrist extensors (bending wrist back) will also help.
Good luck.