Just install the Evilnat CFW PUP again, try first from the XMB system update option, if that will not work then instead use the recovery menu aka safe mode to install it.
As long as you did not install HFW or OFW after installing CFW, you should be fine. If you did install HFW or OFW after installing CFW, then you have lost your jailbreak and will need to use BgToolset again, basically treat it like a fresh console.