Will Apple accept my trade in if it has cosmetic damage?

You’ll want to ask Apple for the official answer.

In general, Apple cares about function, physical structure, glass, and related details, and less about strictly cosmetic damage. Bent or broken or swollen or not working is usually Bad. Minor scratches and scuff marks are usually acceptable, though might or will reduce the offer.

But again, only Apple can provide the official answer here.

You can do a trade-in at a local Apple Store and the staff will review the device on the spot, if that’s an option for you.

For some little damage, it can be eligible for trade in but the price you're getting for it can be lower

Only Apple can tell you how much it may be worth. You can be assured, it won't command the top trade value, if they do take it in trade.