do you think that if i put no-follow on some of my internal links in the index page it will have any effect on PR of the index page or other pages
The "no follow" prevents search engines to be index the link. If you want your link to be indexed, please don't put the "no follow". I think that the "no follow" has no effect to the PR.
there are a lot of internal links in the forum are nofollow so the question is will this have any effect?
A forum really is for traffic. You would have to do an awful lot of posts to help serps. Some would say that forum posting is ineffective as well as devalued by G
i am talking about using nofollow tags in the internal linking in the forum. like here in dp there are a lot of internal links that have nofollow this is also in a lot of other forums and websites. again i am talking about internal links i want to know that if i use nofollow in some of my internal links will it help boost my other pages
Yes many large well SEOed sites are doing this. Their about page and any others you don't need to rank highly in the SERPs it stops the spread of PR to pages who don't need it and keeps it within your important pages.