Thanks for your question.
I do understand your concern due to the sudden onset of your swelling.
Since, you also have stiffness & more pronounced in ring finger it does seem to be related to inflammatory process likely arthritis conditions like rheumatoid arthritis, or other connective tissue disorders.
In the absence of any weakness of the hand, this unlikely related to nerves or blood vessels.
You should take 800mg ibuprofen 3 times a day with food for next 48 hours.
If there are no other additional symptoms, then the swelling should improve with time.
Also use cold ice pack to reduce the swelling over fingers for atleast 5 minutes 2 to 3 times a day.
Yes, if it does not go down in next 48 hours, then you should see your doctor.
It is better to avoid lifting with your left hand till the swelling goes away.