Well, we weren't a wealth of info for you, were we?

You might try a solvent like "Goo Gone."...Be sure you check your fabric for colorfastness first, though.

My only other suggestion is to "iron-off" the iron-on glue! Cover the glue with a cotton fabric and iron again...it might transfer to the cotton. If your jersey is a poly-blend, you'll have to watch the heat setting...it might melt the fabric.

If none of that works....find a new/different crest to cover the spot!

If this will be a situation that you'll face again in the future, just sew the patches on instead of using the iron-on backing. I do this with all our scout patches and badges...at least the ones that get transfered to future uniforms, or will need replaced eventually.

Good Luck!
Lenora