There are many adverse effect of intralesional steroid injection. Hypopigmentation
is common of them but your hyperpigmentation
around the site of injection might be a reactionary/ compensatory state of melanin synthesis.
If you have no other pigmentary disorder of skin or any history of use coloring agent on hypopigmented site then cause can be steroid.
You can try Hydroquinone
4% preparation/ chemical peel/ laser procedure on your wrist join area with consultation/under supervision of a dermatologist