Help! My lenovo m10 fhd rel is cracked from the inside!

The screen is busted and needs to be replaced in your case.

That said, I can explain your parent’s apprehension — depreciation is cruel to Android tablets. If you’ve had it for a while (1-2+ years, usually) the parts cost vs. used replacement cost tend to line up if you do it professionally and the device is unrepairable and not worth fixing.
However, if you can do the repair yourself then you sometimes stand a chance the average person doesn’t who takes it to a shop. The issue at that point too is even if I tried a DIY attempt, you need to be a little careful since a lot of these screens total out the units as a raw part. Now if you found a FRP locked donor that puts the odds in your favor by a lot, but you usually do not win economically without a donor with most android tablets. In some cases, you need to sit on the device until you can get what you need at the right price.