TB near wrist joint is a rare entity but still can happen.. the change in urine color is due to medicines. It will settle once medicines are stopped.
Have you got any other investigations like X ray, MRI of wrist or any inflammatory markers.
TB medicines have various side effects like nausea, vomiting, change in urine color, etc. but not all patients develop those side effects. It depends on how the body responds to them..
Next Steps
If you want to confirm TB, you can plan for getting a biopsy from the site of lesion.. If he is also having cough, he should also get Chest X ray done to find any involvement of lungs..