How to transition

So I’m installing three-quarter inch hickory and I’ve attached an image to show my problem. I started with room number one and then transitioned into a hallway which is number two. When I started with room number one, the groove was against the wall and the tongue was out facing number two. Now the number one and number two are completed I am wanting to extend into room number three. The problem is the groove is facing into the room and I can’t go backwards with a flooring nailer. Is there any problem with just flipping the first board in the doorway transition to where the groove is facing number two and the tongue is facing the wall and number three? Or is there a better way to handle this at this point? Should I cut a” tongue “ from another board kinda like a spline? Use construction adhesive for the one board? It would only be for the doorway so it’s small.

Thanks, I’m a DIYer and this is my second house I did so be gentle.

So I’m installing three-quarter inch hickory and I’ve attached an image to show my problem. I started with room number one and then transitioned into a hallway which is number two. When I started with room number one, the groove was against the wall and the tongue was out facing number two. Now the number one and number two are completed I am wanting to extend into room number three. The problem is the groove is facing into the room and I can’t go backwards with a flooring nailer. Is there any problem with just flipping the first board in the doorway transition to where the groove is facing number two and the tongue is facing the wall and number three? Or is there a better way to handle this at this point? Should I cut a” tongue “ from another board kinda like a spline? Use construction adhesive for the one board? It would only be for the doorway so it’s small.

Thanks, I’m a DIYer and this is my second house I did so be gentle.