I have ingrown toenail ( infected but no pus or blood) so im soaking my feet in vinegar . now i have small black dot on skin near toenail. gangrene?

Gangrene: would be rare for a young and healthy patient to get with simply soaking in vinegar for a short time... however, if a patient has limited blood supply and/or has neuropathy in the feet, then the chance of gangrene is exponential. A picture or exam would give you the best diagnosis and treatment plan you may need!

You state: Your 20 so I would highly doubt it is gangrene. If its infected, just to see a foot doc and have it taken care of correctly.

Blood Blister...: I'm thinking that that small black dot on the skin, near the nail is probably a very small amount of blood trapped under the skin. Leave the spot alone and keep an eye on it. Have the ingrown toenail treated by a specialist. The fix is usually performed in the office with minimal disruption of you life.