I just noticed my partner (male, 23) has a crackle under the skin on his lower back, left side. It's been there for at least a couple of weeks, but probably longer. I first noticed it when I gave him a massage, and didn't think much of it. But it's still there. He's healthy and it's not painful. Almost feels like an air buble, but one had to push a bit deep to notice. And air bubles under the skin aren't normal..
What could it be? Anything to worry about?