My 7 month baby active and healthy creep and little bit crawl but till now can t sit on his own only supported, worried is it normal?why delay?

Still OK: While not sitting on own at 7 months may be just a little behind in development, it's not terribly delayed yet. It sounds like his other skills are age appropriate for his gross motor skills such as creeping and trying a little to crawl. I would not consider it a problem until 9 months if everything else is going fine. Infants develop different skills at different times - he wanted to creep first!

Normal: The average age for a baby to sit unsupported is 7 months. There is a lot of variability between babies but your baby sounds normal. As long as baby continues to develop skills, sitting better and better over time, and sits unsupported well by 9 months, I would not worry.