since starting nails this has been one of the worst problems ive had. i have lost (never had a chance) to capture YEARS worth of designs...literally 1000's because i could not get a proper picture. now, they make cameras that can capture detail...(thank god) but, you still have woes.....here is a solution.
put a sticky note over your flash. make sure its a white sticky note. take a picture..if there is glare, add 2 sticky notes..if there is glare, put 3...........adjust your lighting until you see how sticky notes take the basic glare off of the nail when you are shooting it.
this small tip..............has helped me IMMENSELY.....MORE THAN MOST ANY OTHER.....i have sticky notes everywhere near my camera and there is not one day that goes by where im not looking for sticky notes to adjust glare..........i hope this helps you as much as it has me.
love and light