There's a name for it called mother's wrist and it occurs commonly during and after pregnancy due to hormonal changes, fluid retention and lifting. You may see a sinseh to see if it helps before heading to a doctor. GPs will likely prescribe anti-inflammatory medicine. https://en.wikipedia.org/wiki/De_Quervain_syndrome
It's pretty common among mummies. DeQuervain's tenosynovitis (mummy's thumb) - pain between the thumb and forearm. I went to see a Chinese Sinseh after my confinement but you can try wearing a thumb splint wrist support to see if it works for you before heading to the doctor.
thanks
JessieGal