My left index finger is swollen on top and its itching and paining, it looks like a blister but i didnt burn. what could it be? should i see a doctor?

Possible allergic: The itching may be related to an allergic reaction. Apply topical low dose steroid cream twice daily and a topical antihistamine for relief. The other causes include a fracture and swelling.

See your Dr: Swelling, pain and itching anywhere on the finger can be a sign of infection. Skin infection is called cellulitis. Have an in person exam by a Dr to determine what the likely cause is and receive instructions/medications for treatment.