Having wrist pain (under the thumb), especially when moving the thumb or writing. but can't stop writing as am a student

Repetitive stress : If someone performs the same activity for too long, a repetitive stress injury (rsi) may occur. This happens to intense writers and keyboard operators. Best treatment for rsi is to stop doing the repetitive action, then restart at a more gentle level. It's also helpful to change or improve the posture/position for the activity. Nsaids (ibuprofen, naproxen, aspirin) can help.

Wrist tendinitis : At the base of the thumb especially in what is known as the first dorsal compartment, an entity commonly known as dequervain's or stenosing tenosynovitis of the radial stylojd can affect thumb motion, wrsit motion and writing. Ice, nsaids, soft splints and at times an injection can help. Other issues may be joint pain, nerve pain or just fatigue. Grips on a pen can help too.