Borewell related issue

Just want some information.

I recently had a borewell done at my home. I was suppose to dig a borewell upto 120ft, the starting process was extremely easy as 40 ft was digged very easily with water been available at 40 to 45 ft ,but further during the drilling process they drilled another 20ft in which the shaft of the machine was struct and gravel and sand were falling on the rotating shaft and thus tightening the drilling process. My concern is can I dig a little more upto 100 ft or will the gravel and sand block my borewell. Also can I re-dig the borewell upto 100ft Please suggest and help me sort this issue.