The blinded condition states (emphasis mine):
A blinded creature can't see and automatically fails any ability check that requires sight. [...]
Meanwhile the Divination Wizard's Portent feature states (emphasis mine):
[...] You can replace any attack roll, saving throw, or ability check made by you or a creature that you can see with one of these foretelling rolls. [...]
It seems clear to me that a Divination Wizard could not use the Portent feature on another creature while the Wizard is blinded because the target would no longer be a creature they could see. However, I'm unsure how this applies when changing one of the Wizard's own rolls.
Can a Divination Wizard really use the Portent feature while blinded but only on their own rolls?