9 years after under eye and nasolabial fold filler, could it still cause an infection this far post op?

An in person evaluation is needed to determine what may be causing your concerns. It would be uncommon for filler injected nine years ago to still be present and causing issues. A board certified plastic surgeon should be able to give you recommendations after an examination.

Given the amount of time that's passed since having filler placed, it's unlikely that it is infected. However, even hyaluronic acid-based fillers can cause nodules or granulomas to form. This may be what you are experiencing.

See a local dermatologist or plastic surgeon for evaluation and management.