There are three main reasons for swelling of the left finger. 1. Trauma to the finger, such as heavy objects or finger strains, resulting in damage to the bones, joints, joint capsule and surrounding soft tissues, can lead to localized bruising and swelling, resulting in swelling of the finger. 2. Excessive activity of the finger leading to strain, such as lifting, carrying heavy objects for too long and exerting too much force, can lead to localized soft tissue strain. This may lead to local soft tissue strain, and over time, local inflammatory lesions will be formed, resulting in inflammatory edema, especially after the cold will lead to a decrease in blood circulation, resulting in an increase in the accumulation of metabolic products will also lead to finger swelling. 3, due to the bite of mosquitoes on the finger area, after the bite in the local allergic inflammatory reaction, there will also be an increase in osmotic pressure, the local formation of swelling. The situation.