Bunions can hurt for several reasons.
Pressure and irritation. Pressure on the bump itself from shoes, as most shoes don't allow enough room for the protruding bump or bumps on both sides of the foot. In these cases, the bunion bump becomes irritated by the shoe rubbing and can be inflamed and painful. This is the most common symptom.
Big toe joint. The abnormal big toe position causes damage to the joint and its cartilage, causing jamming of the joint, arthritis and pain.
Hammertoe formation. Sometimes, a bunion can create a hammertoe on the second toe from the big toe impinging on it. This hammertoe can cause pain from the shoe rubbing its top as it sticks up in the shoe, and from the damaged and inflamed joint that results from the deformity.
Gait alteration. Bunions can change a person’s gait due to the abnormal shape of the forefoot which destabilizes it, reducing its ability to function normally. This change in gait can cause pain in the foot, the knees, hips, and back.