Yeah, the only way to 'repair' that would probably be to braze or weld a sleeve over it.

It looks like a big dent, though. I am going to go against the grain here... while cheaper bikes generally have thicker tubing, a dent in thicker tubing will actually mean the material is more stressed than a similar dent would be with thinner tubing. The reason is that as a thicker item bends, the material on the outer faces needs to deform more than it would on thinner material (think aluminum foil vs the quarter panel on a truck), and so it is more like that there is or will be some type of crack or failure beginning on one of the the surfaces.

I would personally send that back, but I would say you still have a fair chance of getting years of trouble free riding out of it. You also have a small chance of landing teeth first against a curb.

Edit: On second look, the crack is not too bad - I have certainly ridden steel frames with worse dents. My comment about the stress involved in bending thin vs bending thick material stands, though. And you still have an increased risk of failure, but I would guess not too big a risk. Please take all comments here at the same value you should give to every opinion on the internet (~=0). Use your better judgement and inspect it regularly for anything that looks like a crack, and if you see a crack, stop riding it immediately. Start putting money in a jar to be ready to buy a replacement frame (Many similar quality frames are $100 or less from internet vendors). If you plan to use a 'swear jar' system to save the money, I'll get you started... **** **** **** ******* with a bannana and then **** the **** out of that mother****er with a ****ing ********** ****rag ****** ****.

You're welcome!