My husband is constantly ripping his belt loops out of his blue jeans. (Well, maybe not constantly, but it feels like it is!)
So, here is my method for repairing it. (It's not the bible on jean repair - just one idea on how to do it.)
First, cut a square of denim a little bigger than the hole. (I cut it much bigger because I wanted to be fast and not have to be careful of placement.)
Zig zag (or serge) the edges - or just let it fray inside your jeans - it'll get sewn around the hole.
I always save pieces of old jeans (usually the legs, or sometimes I just throw the entire pair into my box for repairs later) - if you don't have old jeans in your scrap box, you can buy a jeans patch or you can use some other fabric (it won't really show through under the belt loop - and under a big hole on the legs it could be decoration!) - or you could go to goodwill and grab the first $1 pair you can find, wash them, and use them for repairs.
Place the patch on the INSIDE of the jeans to cover the hole.
Hold it in place and stitch around the hole. (As close to the hole as you can will make it less visible.)
How it looks on the inside (yeah, I cut way too much) :)
Now, put the belt loop back where it should be. And sew it down.
I sew back and forth (straight stitch) and then some zig zags (again, going forward, then backstitch) - that stitch is NOT going to come out again. :)
How it looks on the inside.
How it looks on the outside. (Done)
Works for holes in other places too.
Doesn't take care of erasing the hole, but it makes sure the hole doesn't get any bigger and that whatever might be under the hole is covered.
I would say I do this to my son's jean's knees...but I don't - I just let them go until summer and then we buy new jeans before fall (he's still young and growing) - and he likes a hole in his knee. 10 year olds...go figure. :)