There is also an app called Apn backup and restore... U could try this and backup Apns from stock and restore on custom rom
The thing is, i installed CM 10.2 on stock slot, so no more stock rom. besides, i should explain more clearly what the issue is with APNs. the actual problem is that when i create a new APN in its settings page, after saving it, nothing appears in the list. so looks like it doesnt save it.