It sounds like you had a spontaneous capillary rupture.
This can occur in otherwise healthy people, but can be also related to thyroid dysfunction, liver disease or nutritional deficiencies (ex. vitamin C). You should consider seeing your doctor to check for these problems unless this has been done already.
There is also a condition called "blue finger syndrome" which is more common in women. It involves sharp pain, then the painful area turns blue (presumably due to venous capillary rupture) and may become numb. Symptoms resolve usually within 3 days or so.
You may be suffering from this condition, but you need to see your PCP for the definitive diagnosis.