problem in Apachi to Nginx Migration

I am not that good in wordpress, you guys can consider me as newbie in WordPress. but i do have good experience in Linux.
I have been trying to shift my wordpress’s back end webserver from Apache to nginx. which i even did successfully and site is loading fine. but there are few icons that are not showing up such as icon-Facebook icon-twitter and other social network icons. they are showing up as a rectangle box.

can you guys please help how can i fix this. after some initial findings with google i found out that this issue is related to fonts or CSS but i am really zero in this regards. any help/guidence will be highly appreciated.

Thanks,
Yousuf