Thanks, everyone! The rubbing alcohol worked once I scrubbed my finger with a washcloth soaked in the alcohol. I don't use it for basting since I glue baste, but I spray basted my very first quilt with it and it was a miserable experience. Still have the silly thing around and I wonder why every time I look at it!
I sure felt silly having spray baste on my thumbnail so I thank you all wholeheartedly for the advice.