I understand your concerns. From your description it appears that you are having a thrombosis/hematoma
at the site of blood prick. It is nothing serious and will definitely resolve in 2-3 days. You can apply thrombophobe ointment over the bluish discoloration. There is no need to feel concerned. You should be concerned only if there is pain even after 2-3 days or if there is any active bleeding.
Hope I am able to solve your concerns,
Thanks and hope you get well soon.