I can understand your apprehensions. X-rays are unable to detect any early changes of osteoarthritis. The pain starts years before appreciable changes can be detected through X-rays. A repetitive tendon injury is a likely diagnosis. Also, it could be osteoarthritis since you have pain in both thumbs. Another possibility is rheumatoid arthritis. Both can cause symmetrical joint involvement.
The treatment is rest, physiotherapy, occupational therapy, and non-steroidal anti-inflammatory such as Tylenol, Aleve or Mobic. Take care!
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.
Hi. I am not a doctor but have disk degeneration in my neck and what can cause thumbs to lock, feel pin prick pain etc, is your c6 and c7 area in your neck causing you issues. With your head on that slight angle looking down, I would think it is more of a referred pain. If it was repetitive injury, then why didn't it take the other thumb long to play up. It's more likely disc inflammation in your neck at those levels because your head is now being held on both sides for long periods.
I have you been evaluated for carpal tunnel? My Mom had it and it was primarily her thumbs that were affected.