i could just take the sim removal tool, which comes with the oneplus one and use that to pry the pins back up through the holes in the metal simcard cover without the cover needing to be removed. so for me the procces was easy to do, and the only thing i needed was a small philips head screwdriver.
probably not relevant to the original poster of the topic, but maybe to someone experiencing the problem now, and to stumble across this post when searching what to do (like myself just 10 minutes ago)
i hope this helps