My right thing is numb from knuckle to above joint. the tendon is tender and i think causing the numbness. it is very sensitive. what could it be?

Finger discomfort: A nerve impingement causes numbness but usually not marked tenderness. An inflamed tissue causes marked tenderness and may cause associated numbness if near a nerve. Any history of trauma? Observe for redness or swelling which signify infection. If symptoms persist or worsen consult a hand surgeon for diagnosis and treatment. In the meantime apply warm compresses and take anti-inflammatory(Advil)