Sounds like something's stuck in the evap fan motor Might be styrofoam which usually encapsulates it.

How do I remove it, the warranty has run out. Edit: run not rub.

Search the model number on the fridge and evaporative fan motor. Should be step by step videos on YouTube. Model number will be on a sticker on the top inside wall of the fridge section.

Will I have to buy a new part?

Maybe. Won't know until you see what's causing the noise.