The bolts/nuts that fasten the chainrings can be replaced and any bike shop should have a set.

From what I can tell from your picture, you cross-chain a lot, that is you often ride in the small chainring and the smallest cog and that causes the chain to rub against the inside of the big chainring. That's what did the damage and also caused the chain to come off frequently in the past. Replace the bolts and nuts and avoid that gear combination. You can get the same results in the big chainring and a larger cog.