Is there a way to get in or I have to go back to increase my lockpick skill? Thanks! I tried all doors and all the doors lead to my objective is locked.

Outside the Crawler? You have to go into the Control Tower and activate a terminal to open the door on the Crawler.
Inside the Crawler? There's a keycard on one of the Enclave officers and also a mainframe in the middle of the Deathclaw Research Facility which opens doors.