I took aspirin and it 100% caused my nipples to grow bigger. The answer most people say is "eat more". Okay.. I eat more milk and my scalp gets itchy. The answer there? Not enpugh calories and you are hypo.
Here's a possibility, maybe you had gynecomastia before but because your core body temperature was low you, didn't notice it. After taking aspirin your temperature rose and it became more noticeable ? Isn't it well know that when people are cold that part of the bodies decreases ?