5year ago i get hit by rod in my back of head that time i got round little dent no pain no swelling that time,is this dent is in skull i am worried after5years now without any reason is this dent goes away with age and is this fixed now if it is skul?

This “dent” was most likely soft tissue and not a deformity of the skull. There is motto worry about after five years.

What you likely had at that time might have been a Scalp hematoma (just a little blood clot). However, your body absorbs that in a very short while and you have no permanent deficits or deformities because of that. It doesn't seem like a skull fracture from your description and even in the extraordinarily unlikely event that it was, it is all well-healed by now. So, no worries!