The original plan was for Finland and Sweden to join NATO at the same time. It has since become clear, however–due to opposition from Turkey and Hungary–that Sweden and Finland will not be joining at the same time. There are separate Accession Protocols for Finland and Sweden, each of which has to be ratified separately by all member states. While all the other member states ratified both protocols together, Turkey and Hungary have decided to ratify Finland's protocol now, but hold off on ratifying Sweden's for the time being.
Given those decisions, Finland's accession process is almost certain to be formally completed in the next few days, at which point Finland will be a full member of NATO. But there will now be a period in which Finland is in while Sweden is still out, and we don't know how long that period will last. It is likely that, given a few more months, Turkey and Hungary will be convinced to drop their opposition – but that's only likely, not guaranteed.
Does that mean, once Finland has finished joining NATO, it is going to have to formally sign and ratify Sweden's accession protocol? If every existing member state has to ratify each accession protocol, doesn't that now mean Finland has to ratify Sweden's as well? And normally, to ratify something, you first have to sign it: will they have to formally reopen Sweden's protocol to add Finland's signature?
I have no doubt that, if it is required, Finland would promptly sign and ratify it – politically, Finland is a strong supporter of Sweden's membership – my question is only about the legal formalities involved.