Hi there!
Well, without an evaluation it would be difficult to determine the cause of your symptoms. If there has been no injury, possible causes could be infections, inflammations, degenerations, growths like spurs etc, nerve impingement/ compression, peripheral neuropathy, ischaemia etc. It would be best to get this evaluated by an orthopedician for an accurate diagnosis and appropriate management. Meanwhile you may try resting the ankle for relief.
Hope this helps.
Take care!
It could be Bursitis maybe.... Bursitis is inflammation of the fluid-filled sac (bursa) that lies between a tendon and skin, or between a tendon and bone.