Hello boy is 7 months nw.yet he hasnt started to crawl.its worrying.please help me in this

It's completely fine. Every baby is different and will achieve milestone differently. Lots of babies starts crawling by 9-10 months. And few skip crawling too. Crawling is not a necessary milestone. So relax

Each child will be different in reaching milestones so don't worry. Keep some coloured toys in front of him so that he gets excited to catch them and starts crawling.