Im stuck in the Mass Fusion Quest please help

Spoilers ahead! Sooooo i started the Mass Fusion Quest on my Ps4 and chose the Institute. They teleported me up there and i fell down with my power armor and survived. I didnt realize i had to load my old save to get back up there and i started to roam the building and clear it. I then did some sidequest before i realized i cant go back up there and now i played like 10 hours and cant go back without starting a whole new game. Is there any way i can get back up there? Pls help this sucks :(((