Since we decided last year to buy a sewing machine, I thought I could try and do it myself. It is very easy and hardly noticeable once the patch is made.
You will need a pair of jeans to fix, a jeans patch a bit bigger than the hole (+2cm, 1 inch) and thread.
There's a trick about the thread (thanks mum), use grey or light grey thread. Using blue thread, even if it's the same colour as the jeans will produce a noticeable patch.
Place the patch on the inside of the jeans and secure it with pins, take care to stretch both the jeans and the patch.
Load the top thread with the grey coloured thread (the under carrier is not so important), select a wide zig-zag stitch (5mm width) and reduce the length (advance) to 1 to 2mm (a bit like the bottom right stitch of figure 2 here).
Lock both fabrics under the zig-zag presser foot starting from 2cm/1 inch outside the hole to cover, sew until 2cm/1 inch the hole end. Repeat in reverse.
When you reach the place where you started, move the needle to the top most position, release the feet, move the fabrics 5mm (about the width of the stitch) to the side, press the feet and repeat until the hole is covered.
Here is the patch finished. The good news are it is hardly noticeable, the bad news are, that usually if you do this in one leg, chances are the other leg's fabric will also fail in a few weeks.
