I've been shooting this bow for years and doesn't effect the performance at all.  But I'm selling some of my bows and thought I'd check first to see what it really is.  Is this a glue problem or just cosmetic?    

What part of the limb is it? Towards riser or tip?

hard to tell without seeing it in person but it doesn't look good to me.

Back of the bow on the riser 2" from the bottom of the leather grip.

Looks like a glue separation to me. I had one that did that--got basically air bubbles where the glue did not adhere well to the oily lam wood.

Yep.  Looks like a glue starvation area.  Probably hold together for a long time, but eventually it will expand, and it may delaminate.  Is it separating on the edge now?  If so, might be able to drizzle some epoxy into the area.

Sand off the finish on the edge in that area. Spray of with air gun and wipe with denatured alcohol and let dry. The see if ya can get some ca thin glue to run into the lift. Then reveal with some finish. It will at least keep moisture from creeping in. My last ten shots or 10000 but at least you will have tried to save it.

Cory

Yep.  What Cory says.

Can you hear the bow make noise when you draw it? If you can, it won't last long. It'll sound like little tinks.

You might try sanding the area and clean with alcohol and use some Loctite 420.Very thin CA glue and may seep in if that is separating alittle.

No noise when I draw and it hasn't grown at all.  It's like it has always been there but of course it hasn't.  It didn't start small just appeared one day.

I would take it to a Bowyer and have him check it out. Looking at a picture is way different than in person.

Be careful!  I had a bow that looked like that once, it delaminated on the belly side of the upper limb.  When it delaminated the glass went into the web of my left hand between the thumb and pointer finger, through he meaty part of the hand, and you could feel the tip just below the pinky finger bulging against the skin.  I was extremely lucky none of the tendons were cut and I didn't lose the ability to close any of the fingers.

Personally, I'd cut the bow into pieces, throw it away, and move onto my next bow.