I had dents before, I used flaxseed oil and this exercise I created [ok probably not lol 
] to help fill them out.
Lie down on stomach on your bed or any surface
Lift both legs at knees, so your in a sideways L shape
Keep knees together, separate your legs in a V shape as far as you can making sure to keep knees together!!
Bring legs back to starting position
Repeat 50 times for the first week every day
100x Week 2
75x Week 3
100x Week 4
Along with flaxseed oil, the dent should begin to fill out completely within 2-3 months.
] to help fill them out. Lie down on stomach on your bed or any surface
Lift both legs at knees, so your in a sideways L shape
Keep knees together, separate your legs in a V shape as far as you can making sure to keep knees together!!
Bring legs back to starting position
Repeat 50 times for the first week every day
100x Week 2
75x Week 3
100x Week 4
Along with flaxseed oil, the dent should begin to fill out completely within 2-3 months.