You'll remember things more than you think, even though it doesn't seem like it when you just casually try to think about an old topic. If it's really worrying you, try doing some flashcards (devote like 30 minutes every day to reviewing old material - you'll thank yourself come step time). or reading through the relevant material in FA.
Yea don't stress. The important things from 1st year will be reiterated and probably make more sense in the setting of pathology.
Also this never ends, you'll forget things from 2nd year in 3rd year and things from med school in residency, etc. Trust the process, know you can always look things up, and the things that will be important in the long term you will see repeatedly.
I'm always a little bit glad to read that this happens to other people as well. Sometimes I get nervous i'm the only one who can manage to take 2+ years of spanish in high school and now only remember "hola" and "como estas". lol