Knocking noise machine is knocking [against something] and not making any stitches. I slowly turned the knob to try to see what's hitting, but to no avail. Thanks in advance for any response,

feed dogs, bobbin case etc could be packed with lint. Also needle may be slightly bent.

check that a bit of the broken needle is not interfering with the bobbin case movement
if the breakage was hard enough it may have altered the needle / hook timing which will cause a knocking sound as well

check thread and make sure thread has been in its threading slot in your bobbin case

If the buttonhole dial has been rotated so that its indicator mark is not at zero (vertical aligned with the plate indicator mark), the stitch width dial will not function. Turn the buttonhole dial clockwise to the vertical mark.
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Sounds like your needle is hitting the needle plate instead of going through the tiny hole down to the bobbin. Try using the handwheel slowly and watch. Or perhaps the needle is hitting the bobbin case. Something has been knocked off the straight I think. Has your machine been dropped or dmamaged?

it sounds like you knocked the machine out of time & it will have to be taken to a
sewing machine shop to be retimed

try these sites

sewingpartsonline.com
sewvacdoctor.com
whitesewingcenter.com
sewingpartsdirect.com
sewingsupplywarehouse.com
sewforless.com

there are generally two variable controls .. one adjusts the stitch length (distance between stitches measured in stitches per inch) ... the second is stitch width .. that adjusts how far the zigzag moves left and right .. thats usually just a number from 0 to 10 or so .. 10 would be maximum width .. 0 would be used for straight stitch ..
so you need to adjust the stitch width control to make the stitching narrower .. the controls are called different things on different brand sewing machines .. if you have the brand and model number then there may be instruction booklets available ...

If the machine does not knock when in straight stitch then it is the stitch width limiter. You would have to take off the side cover with a T20 torx screwdriver. Once open you will see an elongated U-shaped piece with a screw through the bottom of it (its maybe a half inch long or so). Its just above that big bottom thread guide. I think you need a T10 torx driver, loosen that screw and move that u-shaped part slightly (very slightly) so it isn't hitting anymore on the side to side action. It happens but can't really harm anything.
I'm sure thats it.

sounds like something is broken. best to get it checked out. take to the sewing machine doctor.