Mix up a little of the two part epoxy and smooth it on with a fine paint brush and she'll be sorted. The blank won't be compromised from such a small defect.

Use masking tape to confine the area you want to repair to prevent getting epoxy everywhere.

Looks like its a reasonable way up the blank, If it was close to the tip it might be a different story

 Thanks guys, I'll give it a go...

I'd just use some 2 part epoxy (araldite). but looks like its all the way through the wall of the blank so wear sunnies and be prepared to have the rod snap - its a possibility (i'm assuming its a graphite blank//)

 It's a calstar 300h

with the epoxy a stated but then put a bind over the area and epoxy again..

The damage looks deep.

As stated above, epoxy and an overbind would probably be the bet way to go, but epoxy wont flex like the blank.

A repair is a bit of an unknown, remember that if the repair fails, it will fail when you have a BIG fish on.

I'd bite the bullet and replace the rod.

Yes and Yes to the 2 posts above.

I had a rod snap that had a similar area of damage, maybe smaller that the one on your rod.

It broke while hooked up to a huge Cod. I did manage to get the fish in which was quiet a feat on half a rod...lol

I would look at a replacement if I were you ..

 Being a Calstar I think it's worth a repair. I had a cheaper rod which had shattered the blank at the butt guide. What I did was to fit an inner sleeve overlapping the shatter by about 10mm both directions and epoxy in place. While that's wet I put more epoxy on the outside and bind over with size A thread. The epoxy will squeeze out but that's fine as when finish binding you just wipe excess off. When epoxy set paint rod finish epoxy and that's it. I hooked up a big ray on my repaired rod which I played with for over half an hour and the repair held. Now, use 24 hour type epoxy as the 5 minute one is not as strong and doesn't give you enough time for binding while epoxy is wet. If you use grey thread close to the colour of your blank it'll be difficult to tell where the damage originally was. Using size A thread can give a very good finish as the threads won't be obvious. In your case I would probably only use thick brown paper as an inner sleeve as this is to stop the epoxy from seeping all in to the blank rather than stay put. If this doesn't work then only buy a new rod. For someone like me who has the stuff the cost of repair is only a few $

 Spew....

Could probably smooth on some glue but be sure on attempting a proper fix myself, as the Id probably turn the calstar into an uglystik.

Is it worth taking it to a shop to assess?

 No loss in getting a tackle shop to assess but I think it's worth to attempt repair yourself. I think the only thing you don't have is matching thread. If you dont want to inner sleeve then at least bind on thread with epoxy. Don't use epoxy alone. Bind thread at least 5mm past the scratch. At a pinch you can use sewing or embroidery thread but these need to be sealed prior to painting rod binding finish. Before you epoxy and bind clean the area with alcohol or turps.

There's a guy, Jim Head, in Westminster who's selling up all his rod building gear and he had a huge variety of thread and good quality like Gudebrod. Pick up a spool from him for $5 or something like that. Don't know if he has time but he can also repair. He's been advertising on gumtree