Wilsonara Hilda Plumtree Purple Wings
 

Watered this last wk and its still wet, its getting more sun that it was before so Im wondering if its too cold.. This has happened in the last couple days and its not been that cold here in Ohio.

Oncidium Hilda Plumtree has a lot of cool/intermediate-growers in its background, so unless it's going below about 50°, I doubt that would be an issue.

Personally, I'd remove that leaf altogether, dust the wound with cinnamon, and be done unless it progresses.

If you can provide more info about your culture, maybe we can conjure up other potential explanations.