open source it and document it well. itll prove whether your library is valuable enough to others to leverage. You can put up a donation button for a buck. Selling the source of a tool to someone whos never used it is basically impossible. You need to garner interest first.

alternatively come up with a payment model that allows users to get familiarized for free and then commit to pay when they want some niceties, although you said youre done coding so i doubt youll want to put in that work.