How are recurring boils on the buttocks normally treated?

You’ve likely got chronic urticaria, and will need to take a doctor-prescribed course of anti-histamines to get rid of the itchy rash. No cause or trigger is found in 80% of people with chronic urticaria, in case you were wondering. It’s just one of those things that happen, unfortunately. Good news? It’s self-limiting, and responds very well to treatment (oral anti-histamines). The dents in your nails sounds like nails pitting (shown in picture below). There are several causes for nail pitting, of which psoriasis is an important cause to rule out.

Exercising a particular muscle overtime does cause the muscle to grow (hypertrophy), and simply put, become more prominent though firmer. Much of the bulge, however, can be due to the overlying fat. As such, muscle growth beneath the fat without appropriate attempts at losing the fat can indeed result in a more prominent buttock. I would advise adhering to a good diet that is pro fat-loss, together with a lower weight, higher rep count and equally frequent cardiovascular exercise to promote fat loss and muscle toning. The lower weight count will also do your back a huge favour in the long run.