If i hit my head when i was younger can it cause a permanent bump to be there for the rest of my life. ?

Unlikely,: as a bruise/swelling under the skin from trauma (aka hematoma) should resolve with time. It might be a good idea to see what that "permanent bump is". I'm sure it is nothing serious but it would give you peace of mind. You should get a physical exam. Best of luck.

It's possible : Many bumps and bruises can resolve completely over time. Some injuries can cause permanent scars or bumps.

It depends: on how hard you hit it, and how big the bump is, but it is possible for a hard hit to any bone (including your skull) to cause some permanent swelling or thickening to the area that was injured. It matters how big it is, the location of the bump, and does it bother you or not. This is one of those items where one look is worth a thousand words, have a doctor examine it.