Welcome at HCM.
It will be my pleasure to help you.
The dimples which are present at your lower back are just the normal land mark of our joint which is known as sacro iliac joint-
This is present in normal person.
The knot which is present near by this looks to be a inflammaed connective tissue
& at this stage better termed as FIBROSITIS
.In your case this may be due to your dance & rolling habit.Most probably this had lead to injury
at this area which had healed with fibrous tissue.
You should not bother about this & should consult to a orthopedic doctor for this.
Your doctor may give you a good anti inflammatory analgesic
& may use a local steroid
injection to give you relief.
Hope this will help you
Wish you a happy & healthy life.