Bumps at the great toe joint can either be a condition known as Hallux Limitus/Rigidus which is caused by an arthritic process within the joint. Over time, the arthritis worsens and to limit the pain, the bones grow spurs to limit the motion in the joint. These spurs are usually on the top of the joint. If the joint moves less, there is also less pain!
If the bump is seen more to the side of the big toe, it is likely a bunion or Hallux Abducto Valgus. The bunion is not a bone spur as described above but rather the bone right behind the big toe joint starts to lean out and looks like it is a new bump.