Medical attention for a swollen left arm is recommended if swelling is accompanied by pressure, squeezing or fullness in the chest, which could indicate a heart attack, states Mayo Clinic. Medical attention is also recommended if there is a protruding bone in the arm.
If medical attention is not required, attempt to reduce the swelling by rest and applying an ice pack, along with compression and elevation, according to WebMD. Avoid hot showers, hot packs and anything else that promotes swelling for 48 hours. If arm pain continues over several days or the swelling gets worse or does not improve, seek medical attention.