Well obstructions can hinder your ability to extract water from your well and can be a source of contamination, depending on the type of obstruction. Obstructions typically occur when either part of the pumping mechanism becomes damaged and stuck in the well, or when a cave-in of the well borehole wall occurs.
If there is piping lodged in the well, it could become a source of nutrients for bacteria, such as if a pump filter becomes lodged in the well, the filtered material could provide a suitable place for harmful bacteria to grow. Or if old iron piping is left in a well, iron bacteria could become a problem where there was none before.
When a well wall caves in, it typically indicates that there was some void or cave present close to the well. Depending on the geology of the surrounding area, this could introduce contaminants or allow for foreign objects to enter the well, on top of the fact that the cave-in may have damaged the pumping equipment or could hinder future pumping
If you think you have an obstruction in your well, contact a certified well driller to remove the obstruction and check the wells integrity.
 
In the above video you can see abandoned well piping.
  
 In the above video you can see a cave-in of part of the well wall.