High Pitched Scraping Noise From Fan

I have a dell Vostro and last year I had a problem with my fan when it made a loud screeching noise like I told sounded like scratching. I went to get it repaired and it was fine. Now 1 and 1/2 years later I have the same problem of the sound. I don’t know if it’s a physical problem or something I can fix by updating something. I have tried to blow particles out but nothing changes. It mainly happens when I move it but it still buzzes when it’s idle on my desk. Coincidentally it happens when I have school exams on so if someone can respond ASAP. THatll be great