If it were me, I would only consider locking it in if the Nickel...

If it were me, I would only consider locking it in if the Nickel price wasn't moving around so much. The falling Real is cushioning the falling Nickel price. By locking in the Real price now you limit the cushion that is provided if further falls eventuate.
In this type of environment I wouldn't lock in the Real unless they locked in a favourible Ni hedging price also which is highly unlikely in this market IMO.
If it is possible to lock in a price for both which insured a decent profit margin I would do it until Nickel bottoms. I personally think Nickel will bottom well before the Real does.