Q: The wrong oil was used during my last oil change how will this affect my car

I took my car to the shop so that you can get a oil change and get inspected back in January. About a week after I got the oil change my vehicle started making a knocking sound coming from the engine at first it was low and I paid no attention but over time it progressively got louder I took my vehicle in to get an oil change today which is March 15th and the mechanic there told me I the noise is coming from the engine internally and because of that he would not be able to do a oil change he also told me that it could be because the wrong oil was put into my vehicle as he saw the oil change sticker in my window with the wrong oil grade for my vehicle I am trying to find out if this could be the reason why my engine sounds as if it's grinding rocks or is it not the fault of the mechanic who put the wrong oil in and it could just be an engine problem due to normal wear and tear the oil used on my vehicle was 5 W 30 and I'm being told that the oil that should have been used is 0w 20

My car has 100483 miles.
My car has an automatic transmission.