Bitten by horsefly whole hand swollen skin turns yellow when close hand what can i do?

Horsefly bite: Sounds like you are having a localized allergic reaction to the bite, but may also have an infection developing. Antihistamines may help reduce the swelling, as well as cool compresses, and elevating the hand (prop it up on some pillows), but if there is a question of infection (swelling, redness, warmth) then you need to see your provider for t reatment.