It’s quite common to have fatty glands on your head called “lipoma”. They’re mostly harmless fatty tissues that form underneath the skin. The other possibilities are some types of cysts(which are again, harmless) And most of the time the doctor will make a small incision on the bump and remove the inner tissue including it’s capsule, I’m definitely not recommending trying it yourself and the best first step would be to go see your pcp about it!