Also, When you put back the rivet in you may have a tight link, it happen in most case no problem.

You can use the tooless method scroll down to without Chain Tool http://www.parktool.com/repair/readhowto.asp?id=53

Alternatively you can just put in a square head screwdriver that fit between the place and spread them a tiny bit just enough so it's no longer tight. Don't use any force. Only the sightless touch to loosen the link