No water during drilling of the borewell, however, found water in borewell after four days

We drilled borewell depth of 400 ft, but during drilling we didn't get any water, hence stopped without flushing. However, after four days we noticed borewell filled with water upto 5 feet from ground. Can we get water daily if we install pump or I should go for drilling another well. Since, no pump is installed we observed water level same for the period of three months. While drilling we found mostly stone powder with less clay area, since there was no reduction in water level in summer. I am afraid whether its just a cavity in long stretch of hole in rocky area. will flushing help to open more water holes in well and increase the water accumulation rate?