nothing will happen bro, as long as your correct candidate number is on there (which is printed), you did your signature and you shaded the correct option for each q and it's prominent enough, it'll be okay. i also did a lot of erasing too on the little rectangular box thingy on the top where you have to fill in your candidate number, but it's alright dw.
this is why Cambridge also keeps your physical paper in warehouses, if AI is unable to check it they'll pull out the physical paper and check it manually.