I developed hard, non-painful bumps on the upper ear

I have developed bumps on the upper part of my left ear. They are hard, ball-shaped and non-painful. There are three of them; they occurred about a week ago. Am a bit concerned about it. What could it be?

Once I had the same bump and was positive that they were not pimples. I could not squeeze them and they were painless. I wanted to visit the doctor because of them, but could not manage it. The bumps persisted there and didn’t change in their shape. I tried it to squeeze one again a week after and hard white ball jumped out. Mild redness left but calmed in a short time. I still don’t know what that was but it has never again returned.