Can sleeping on ear cause it to protrude more?
Sleeping on your ear should not cause it to stick out more. I would say that you just have some minor asymmetry between your ears, as many people do.
The short answer is no. After the first few weeks to few months of life, the ear cartilages cannot be easily molded or changed by pressure, specifically favoring one side to sleep. Most people have ears that are subtly different -- this is perfectly normal.
The short answer is "no". Sleeping on your ear will not make it stick out. And you are correct; minor asymmetries are the norm.