Mmm could be from climbing the bars of his cage or just that he is young and moulting. I don't know of any health issues it could be but be sure to give him a mineral block and cuttlefish bone just to be sure.

He's been to a vet before I had him(I've only had him for two months) and the previous owner didn't say he had any problems. He's eight months old. Could this have been from another bird? Also his long tail feather is about to come out and it keeps getting all twisted around. Should I pull the feathers out?