Well could be a bone that is minory injured so it's not affeting your arm movement(not yet),or maybe a ligament problem. The best thing that you can do is go see the doc,make a radiography and that will tell you exactly what rpoblem tou have. Go before it's too alte and you cans till fix it.
Some of the possible causes could be arthritis, infection of bone or joint, related neck pain or shoulder pain or pain in other body parts, frequent motion disorders, intense injuries like fractures, sprains, dislocations and nervous problem. However consult your physician who may order you to take some lab tests.
A likely cause could be either mild arthritis, cold weather, carpel tunnel or tendanitis. Most commonly aching can be associated with cold weather as it effects your tendons and muscles. Try a basic pain and inflammation reliever like Acetomediphine or iboprophen. If that doesn't work contact your physician as it could be something more serious.