Last we left FN-2187 in Star Wars: The Force Awakens he was not doing so well. Following a lightsaber slash to the spine, Finn was deep in recovery while Rey went off to return a piece of lost property to its rightful owner. Thanks to the trailers for Star Wars: The Last Jedi, we know that Finn does not stay this way for long; he will eventually awake from the coma to do battle with his former boss once again. When he does wake up, he won't exactly be feeling calm and well rested. As John Boyega explained:
Finn wakes up thinking he's still in Force Awakens, thinking he's in the snowy forest in the fight with Kylo Ren. The first word he says is 'Rey' when he wakes up, he still thinks he's in the action. He's got a lot of recuperating to do.
When a fighter gets knocked, one of the first things the referee or doctor asks is 'do you know where you are?' Apparently, for Finn, that answer will be no. This will be a super disorienting and stressful situation for the former stormtrooper. He picks up right where he left off, in fear for his life as well as Rey's. Finn came to care about Rey very quickly and deeply in The Force Awakens, and she is really the only thing that made him emotionally invested in the Resistance's fight. He is not really a Resistance member, so when he awakens it will be in a strange place surrounded by mostly strange people. Han Solo is dead and his girl friend (not girlfriend) left on a road trip to find Luke and didn't even bother to leave a note. Best friend forever Poe and General Leia will likely have to anchor him and calm him down. Finn's primary concern will be Rey's safety, so he will need to know that she is alive and safe and they will need to get him up to speed on the state of things.
It's like waking up from a nap that ran too long; you're sweaty, you just had brutal nightmares, you don't know what time it is or where you are. As John Boyega mentioned to Jimmy Fallon on The Tonight Show, Finn will have quite a bit of recuperating to do. I imagine he won't have much time to do it though, since this film will pick up right where The Force Awakens left off. Given the state he wakes in, Finn will probably want to go straight away to find Rey and protect her. Something or someone will prevent him from doing that and he will have to find a new reason to care about this fight.
To find out what Finn's second and third words are after he wakes up, you'll have to see Star Wars: The Last Jedi, in theaters on December 15th. You can pre-order your tickets for opening weekend now.