I fixed a hole in my arm warmers, by using a patch made from an old pair of cycling shorts The thing about lycra - if you just sew it shut it has a tendancy to try pull apart again at the edges and around the stitches, so I put a little patch of lycra on the inside to reinforce it and sewed the hole up over top. The "scar" looks a little Frankesteiny, but that may be due more to my poor sewing skills than anything , its held up nicely, and its not a problem on the armwarmers, but patching like that might create an uncomfortable bump in a pair of shorts?

Then again a team mate of mine has been wearing a pair of shorts with a little hole in them from last years cross season all year long and it hasn't gotten any bigger.