A bunion is a bony swelling at the base of the big toe and often leads to the big toe pointing inwards, towards the other toes.
A bunion develops as a result of the small bones in the toes (the phalanges) moving out of line with the longer bones that run through the foot towards the ankle (the metatarsals). Bunions are common and anyone can develop them, although they are more common in women.
The progression of a bunion may be slowed through the use of wider-fitting shoes or insoles and the pain can be easily managed by using painkillers. The only permanent solution is surgery, which may be recommended if your bunion causes you problems.
Source: NHS choices